s 
615 



Bulletin No. 90. 372 

U. S. DEPARTMENT OF AGRICULTURE, 

OFFICE OF EXPERIMENT STATIONS, 
A. C. TRUE, Director. 
, Irrigation iiivcutlf^atious, Klwood ITIoad, 1<;x|>ert In <;iiarg:e. 



IRRIGATION m HAWAII 



WALTER MAXWELL, Ph. D.. 

Direclar and CJiief CfieyusI, ILnniikoi Erperhneut StalU. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE, 
^19 . 




Gass 


S4n 


Rook 


.M^ 







^ ¥- 5 



Bulletin No. 90. 



372 



U. S. DEPARTMENT OE AGRICULTURE, 

OFFICE OF EXPERIMENT STATIONS, 

A. C. TRUE, Director. 

Irrigation Investtgatloiix, Klwood itioad, Expert in C^liargo. 



^"i-6 



IRRIGATION m HAWAII 



BY 



WALTER MAXWELL, Ph. D., 

Director and Chief Chemist, Hawaiian Experiment Station. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 
1900. 



P0f»«*vi»pf| 



*0 



LETTER OF TRANSMITTAL 



U. S. Department of Agriculture, 

Office of Experiment Stations, 

Was/migton, D. C, Mvemher 30, 1900. 
Sir: I have the honor to submit for publication as Bulletin No. 90 of 
this Office an article on irrigation in Hawaii, by Walter Maxwell, 
Ph, D., for a number of years director of the experiment station 
maintained by the Hawaiian Sugar Planters' Association. This article 
has been prepared in connection with the irrigation investigations of 
this Office. It discusses the climatic, soil, and other conditions as 
affecting irrigation in Hawaii and gives the results of irrigation experi- 
ments, especially with sugar cane, carried on by the author for a num- 
ber of years. It brings out some of the most interesting phases of 
irrigation problems in that Territory, and will form a basis for further 
investigations of this subject there. 
KespectfuUy, 

A. C. True, 

Director. 
Hon. James Wilson, 

Secretary of Agriculture. 



CONTENTS 



Introduction... 7 

Evaporation of moisture from water surfaces and soils 8 

Transpiration of moisture by vegetation 10 

Power of soils to absorb and retain moisture 13 

Salts in Hawaiian soils and waters 16 

Duty of water ,. 18 

Irrigation practice on the Hawaiian Islands ^ 19 

Study of irrigation at the Hawaiian Experiment Station 23 

Distribution of water 28 

Some results of overirrigation ^ 39 

Some general observations 47 

5 



ILLUSTRATIONS. 



PLATES. 

Page. 

Plate I. Exterior view of a pumping station in Hawaii 20' 

II. Interior view of the pumping station shown in Plate 1 20 

III. Fig. 1. Arrangement for irrigating plats at the Hawaiian Experiment 

Station 22 

Fig. 2. A sugar factory in Hawaii 22 

IV, Irrigated and unirrigated sugar cane at the Hawaiian Experiment 

Station 24 

V. Irrigating sugar-cane seed in Hawaii 32 

VI. Lysimeter used at the Hawaiian Experiment Station 34 

TEXT FIGURES. 

Fig. 1. Apparatus used in observations on absorption and retention of moisture 

by soils 14 

2. Irrigation of sugar cane on level land by means of laterals 29 

3. Irrigation of sugar cane on level land by direct discharge of the water 

from the main ditch into the furrows 31 

6 



IRRIGATION IN HAWAII. 



INTRODUCTION. 

The precipitation of atmospheric moisture is very uneven and irreg- 
ular over the surface of the earth. There are zones that are marked 
by annual deluges, and there are vast areas upon which rain rarely 
falls. These rainless areas are not confined to conditions peculiar to 
specific latitudes, but are found in the tropical regions of India and 
Africa, over the wide plateaus of North America, and in other locali- 
ties having widely varying climatic conditions. 

The regions of small rainfall are very generally distinguished by 
lands of great natural fertility. This is due largely, on the one hand, 
to the absence of great rains that leach out the elements that feed 
plants, and, on the other hand, to the relative absence of crops, which 
results from lack of rain. Among the most productive tracts upon 
the earth to-day are regions that were naturally arid, but which have 
been rendered productive by irrigation. These tracts include the 
Punjab and other vast districts of India, the great basin of the Nile in 
Africa, and large semiarid areas that have more recently been brought 
under cultivation in the middle and western United States. 

The failure of the natural rainfall to produce crops may be due to 
the insufficiency of the total precipitation, as in regions in India, 
Africa, and other lands, where it does not aggregate 10 inches per 
year; or it may be due to the seasonal distribution, as in other parts 
of India and Africa, in northern Queensland, and some of the Pacific 
islands, where a heavy and almost the whole precipitation takes place 
within two or three months. In speaking of the agriculture in parts 
of the Himalayas, Mr. Buckley^ says: "Where the rainfall varies 
from 50 to as many as 100 inches in the year, crops grown on the ter- 
races in the mountains are matured in the dry season by artificial irri- 
gation." In some localities in northern Queensland the annual rainfall 
reaches and exceeds 100 inches, j^et the sugar-cane crop has to linger 
through an annual arid period which greatly reduces the yield, while 
upon the Pacific islands of Hawaii, despite the winter rains, many of 
the most fertile lands would be useless without the prevailing practice 
of irrigation. Irrigation, consequently, is playing an increasingly 
important part in modern intensive agriculture. 

1 Irrigation Works in India and Egypt, R. B. Buckley. London, 1893, p. 1. 

7 



The histoiT of irrigation covers methods of applying water to crops, 
inckiding the crudest efforts of the peasant and the great systems exe- 
cuted by governments or corporations, such as are in operation in 
India, the United States, and in the valley of the Nile. Certain of 
those systems are vast, and have been instituted under the pressure of 
meeting great emergencies. To-day India is using irrigation upon a 
stupendous scale in grappling with the calamity of famine. 

Economic irrigation requires the consideration of physical laws which 
were unknown to the authors of primitive methods, and which have 
not been generally observed in establishing the huge systems of irri- 
gation already mentioned. Some of the physical laws which underlie 
any rational practice in the application of water to crops are briefly 
considered in the following paper. 

EVAPORATION OF MOISTURE FROM WATER SURFACES AND SOILS. 

The movement of moisture is constantly going on. The simplest 
evidence of this movement is seen in rainfall and in the evaporation 
from water and soil surfaces. 

The factors that have been given the greatest prominence as exer- 
cising a controlling action upon evaporation from soil and from the 
surface of water are the temperature and the relative humidity of the 
air. This view is amply sustained if the examination is confined to the 
action of these factors during the extreme seasons of the year. There 
is no question concerning the greater evaporation of moisture from 
soils and waters during the months of summer, when temperatures are 
high, and the amount of atmospheric moisture is also relatively smaller 
than during the cold season, when the temperature is lower and the 
humidity of the air greater. This is demonstrated in man}^ localities by 
the excess of water that accumulates within and upon the soil in winter 
and the droughts that obtain in the summer. There are localities and 
regions, however, that are so fortunate as to have the greatest rainfall 
during the season of greatest evaporation and consequentl}^ of greatest 
plant growth. Setting aside the differences concurrent with the seasons 
and confining observations to the relative actions of the several factors 
during the months of summer, it is then found that the temperature of 
the air and the amount of moisture that it contains are not the most dom- 
inant factors in the control of evaporation. As alread}^ said, they are 
factors, but their combined effects do not compare with the effects of 
wind. Not only in the matter of irrigation, but also in the location and 
exposure of reservoirs this fact is of leading importance. In view of this 
the writer carried out a series of evaporation determinations by means 
of evaporators, at the same time keeping a record of the temperature 
and relative humidity of the air. These observations were made as a 
part of a stud}' of the factors that control the rational irrigation of the 



9 

sugar cane on the Hawaiian islands. The form of evaporator used 
was a small galvanized iron pan, li inches deep and having a super- 
ficial area of 120 square inches. The evaporator was placed under the 
covered stand where the meteorological instruments were located and 
between the dry and wet bulb thermometers, thus having the same 
protection from the sun and the same exposure to the wind as those 
instruments. At 7 o'clock on the morning of the first day 500 grams of 
water were weighed into the evaporator, and at the end of each twent}^- 
four hours the weight was retaken and recorded and the volume made 
up again to 500 grams. These observations were made daily through- 
out one year. A second evaporator similar to the first was placed in a 
barn 30 feet distant from the other. The large doors of the barn were 
kept open day and night to allow of air circulation, but an}^ violent 
air movement was rigidly guarded against. The purpose was to secure 
the same conditions of temperature and humidity of the air as those 
surrounding the evaporator placed outdoors, but to eliminate the 
factor of wind. The data furnished hy the two evaporators were 
taken and recorded in the same manner and with the corresponding 
readings of the thermometers. The results of these observations, 
covering a period of two hundred and sevent}' days, reduced to monthly 
averages, are given in the following table: 

Relative evaporation from ivater surface exposed to the vjincl and protected from the loind. 



Month. 



Exposed to the 


wind. 


Protected from the wind. 


Tempera- 


Humid- 


Evapora- 


Tempera- 
ture of 
air. 


Humid- 


Evapora- 


air. 


ity of air. 


tion. 


ity of air. 


tion. 


°F. 


Per cent. 


Per cent. 


°F. 


Per cent. 


Per cent. 


74.4 


11. i 


28.5 


IS.l 


77.4 


11.7 


76.0 


80.2 


27.2 


80.3 


80.2 


11.3 


77.0 


83.6 


22.5 


81.3 


83.6 


10.1 


78.3 


77.3 


25.8 


83.0 


77.3 


12.1 


78.7 


73.8 


30.0 


82.4 


73.8 


12.5 


76.8 


80.4 


24.3 


80.6 


80.4 


10.0 


75.3 


80.1 


23.5 


78.8 


80.1 


9.2 


71.0 


83.2 


23.3 


74.1 


83.2 


9.4 


75.9 


79.5 


25.6 


79.9 


79.5 


10.8 



April 

May 

June 

July 

August 

September 

October 

November ... 

Average 



A relation mstj be noted between the temperature and humidit}" of 
the air and the amounts of water evaporated, but the important fact 
revealed by the table is the constant and great ditf erence in the amount 
of water evaporated from the two pans. The total amounts of water 
lost during the eight months by the exposed and protected evaporators 
were, respectively, 33,480 grams and 14,175 grams. 

The outdoor evaporator lost 136 per cent more water than the indoor 
evaporator. Thi« vast dili'erence is wholly due to the action of the 
wind, to which the former was exposed, and it occurred in spite of 
the fact that the indoor temperature was uniformly 4 degrees higher 
than the outdoor temperature. 



10 

The differences in the amovints of water given off by the outdoor 
evaporator on different daj^s bear some relation to the differences in 
the temperature and humidity of the air. Thej^ are too great, how- 
ever, to be accounted for by those factors alone; they were, in fact, 
largeh^ due to different velocities of the wind, ^j y^aj of proving 
this, we make use of the data recorded during the month of Novem- 
ber. During the first ten days of that month the average daily evap- 
oration, under the constant action of the northeast trade wind, was 
33.7 percent. During the following eight days, when the wind direc- 
tion was south and the air was almost still, the average evaporation 
was only 13.2 per cent. During these eighteen d&js the maximum 
evaporation under a very high wind reached 11.2 per cent, while upon 
another day, no motion of the air being observed, the evaporation was 
onl}^ 8.1 per cent. In the course of these twenty days the tempera- 
ture variations were very small. 

From the determinations that have been recorded it may be seen 
that the movement of the air is the paramount factor in controlling 
the rate of evaporation from water and soil surfaces. Soils whose sur- 
faces are exposed to the action of strong driving winds will give up 
more moisture, and will therefore need more water, than areas in shel- 
tered locations. Water surfaces exposed to the sweep of the wind lose 
heavily by evaporation. Economy of water therefore dictates that 
reservoirs be built so as to have the greatest depth and the least sur- 
face, and that they be located so as to be sheltered from the direct 
action of prevailing strong winds. 

TRANSPIRATION OF MOISTURE BY VEGETATION. 

The volume of water evaporated from the soil and the volume trans- 
pired bj^ the plant during its growth are the controlling factors in 
determining the total water required in the production of a crop, and 
therefore the quantity of water to be supplied by irrigation. 

Water enters very largely into the structure of all living organisms. 
It is not only the agent which makes possible the mobility of other 
constituents of the plant, conveying them from one location to another^ 
but it enters in large proportion into the structure of the organism 
itself. Consequently plants and trees at all times hold a great volume 
of water, the supplj^ of which is constantly replenished by the water 
taken up by the roots and as constantly depleted by the moisture 
given off into the air b}^ means of transpiration. It is these quantities 
that we require to know something definite about. 

Experiments with the sugar cane to determine these quantities have 
been carried on by the writer at the Hawaiian Experiment Station. 
The specific purpose was to determine the volume of water required 
by the cane at different stages of its growth and to come at a rational 
mode of irrigation. The experiment was carried out as follows: Two 



11 

tubs were used, having perforated bottoms, over which pieces of linen 
were laid to prevent the soil from going through or filling up the per- 
forations. One hundred and twenty-five pounds of similar soil was 
put into each tub. The tubs were then .^et into galvanized-iron pans 
containing water. The water was kept up to a certain level, which 
level was slightly above the point of contact between the soil in the 
tubs and the water in the pans. The pans were carefully covered 
with moisture-poof oilcloth to prevent any escape of water excepting 
through the tubs. The volume of water taken up by the soil in the 
tubs and given off was daily measured and recorded and an equal 
volume restored to the pans. The volume of water that the soil could 
absorb and contain — that is, the measure of its absorptive power — was 
48.2 per cent of its own weight. In tub No. 2 three pieces of sugar 
cane were planted when the experiment was begun, and nothing in 
tub No. 1, after which the water given off by each tub was daily 
recorded for the following six months. During the first twenty-six 
days the two tubs gave off like volumes of water, each one evaporating 
during that period 14,220 grams, or 31 pounds. After the twenty-sixth 
day tub No. 2, in which the cane was planted, began to give off more 
than tub No. 1, containing soil only. At the end of seven months the 
relative volumes of water given off' by the tubs were: 

Grams. 

Tub No. 2 159,550 

Tub No. 1 80,240 

Difference 79,310 

The water transpired by the growing cane during the period stated 
was thus 79,310 grams, or 171.5 pounds, and was distributed as follows: 

Water transpired by sugar cane. 



Time of observation. 



May 
June 
July 



Age of 
cane. 



Months. 
1 



Transpi- 
ration. 



Grams. 

860 

6,500 

11,000 



Time of observation. 



August 

September 
October . . . 



Age of 
cane. 



Months. 
4 
5 
6 



Transpi- 
ration. 



Grams. 
19, 800 
20, 050 
21,100 



From these data we learn the weight of water evaporated per given 
weight of soil during a given period of time. More important, we 
also see the volume of water transpired by the growing cane during 
the several months of its growth. We note the increasing volume 
required by the cane during the stages of growth and increase in bulk, 
and these observations are a clear and definite indication of the amount 
of water required in irrigation. When the cane plant is young its needs 
are small in comparison with its requirements at later stages of growth, 
and to apply the same volume during the early months that is demanded 



12 



later is not only sheer waste, but entails damage to the J^oung cane and 
loss to the soil. However, as explained later (p. 46), the increased evap- 
oration from the soil while the plants are too small to shade the soil to 
any extent in a measure counterbalances the decreased transpiration 
in this stage. 

The weight of the cane grown in tub No. 2 by the consumption of 
79,310 grams of water was 568.9 grams of water-free material, con- 
sisting of roots, 31.8 grams: stems, 53.9 grams;, leaves, 483.2 grams. 
These figures show that in order to form 1 pound of water-free sub- 
stance the cane organism transpired 147. 8 pounds of water. 

Attention is due to the behavior of the transpiring plant under the 
influence of given physical conditions. It was previousl}" shown that 
the evaporation of water from soil and water surfaces was relatively 
very small in the absence of wind and during hot, sultry weather. 
This was by no means the case with the cane plants, as the following 
figures show: 

Effect of tveather conditions on evaporation from the soil and transpiration by sugar cane. 



Number 
of days. 



Character of wind. 



Evapora- 
tion from 
soil. 



Transpi- 
ration 
from 
plant. 



June 10 to 23 

June 23 to July 7. 



NE. trade. 
SSE. calm 



Grams. 
5,700 
3,200 



Cr7-ams. 
1, .550 
3,300 



These results were secured while the cane was still very young and 
the transpiration small. Similar results were observed repeatedl}'' 
during the period of the plants' growth. The explanation lies in the 
fact that, although the hot, sultry weather, which obtains during the 
prevalence of the south wind has but a small effect upon water evap- 
oration, it provides the phjj-sical conditions conducive to rapid plant 
growth. With the increased plant growth follows the vastlj^ increased 
transpiration. 

At this place lasij be stated the action of certain chemical elements 
upon the rate and volume of transpiration by the cane. On Septem- 
ber 20 it was noted that the cane in tub No. 2 was looking j^ellow and 
in a reduced state of growth, and that the dail}" volume of water 
transpired had ver}^ largelj" fallen off". This change was believed to 
be due to want of available nitrogen in the soil, it having been shown 
by previous anal3^sis that, while all other required elements were pres- 
ent in abundance, the nitrogen content was unusuallj^ small. Conse- 
quently nitrogen, in the form of nitrate of soda, was dissolved in the 
water that was being absorbed hj the cane. On September 24 the 
cane was transpiring onl}'^ 500 grams of water .daily. Two days after 
the addition of the nitrogen to the water the leaves began to take on 



13 

a vigorous appearance again and the volume of water transpired 
increased until it became more than double on the sixth day, when the 
cane stood up in full vigor and the yellow color was giving way to a 
deep green. At the end of October the transpiration fell off again, 
running down to only 400 grams daily, when a second quantity of 
nitrate of soda was put in the water. The result was practically the 
same as in the first test. The following table gives the details of the 
two tests: 

Effect of nitrate of soda on transpiration of moisture by plants. 



First test. 



Date. 



September 24 
September 26 
September 26 
September 27 
September 28 
September 29 
September 30 

October 1 

October 2 

Octobers.... 



Transpi- 
ration. 



Grams. 
500 
600 
700 
900 
1,200 
1,100 
900 
900 
900 
900 



Second test. 



Date. 



October 31 . . 
November 1 
November 2 
November 3 
November 4 
November 5 
November 6 
November 7 
November 8 
November 9 



Transpi- 
ration. 



Grams. 
400 
600 
700 
700 
700 
800 
800 
800 
800 
800 



These tests not only display the part played by the element nitrogen 
in the plants' growth and the consequent transpiration of moisture, 
but they also afford a clear illustration of the relations of fertilization 
to irrigation — relations which should receive the most careful consid- 
eration in all field work. In time of prolonged drought in districts of 
small or irregular rainfall the application of fertilizers that stimulate 
growth and transpiration is not advisable, since such agents cause a 
rapid exhaustion of soil moisture, after which the crop goes back 
again, its condition being finally worse than had it not been fertilized. 
But after a rain following a period of drought nitrogen should be 
applied at once to help the crop recover lost time. 



POWEE OF SOILS TO ABSORB AND RETAIN MOISTURE. 

It is now necessary to consider the properties of the soils them- 
selves, and to note the nature and differences of those properties in 
different soils and the behavior of different soils in practical irrigation. 

Before making anj^ explanation of the causes attention is called to 
the fact of the great variation in the power of soils to absorb and 
retain moisture. In the discussion of this point conditions, examina- 
tion, and results relating to the Hawaiian Islands only are considered, 
and particularl}^ investigations which have had special reference to the 
irrigation of sugar cane in these islands. Instead of giving a lengthy 
and detailed description of the means by which such examinations are 



14 

carried out, attention is called to an illustration (fig. 1) of the appa- 
ratus used in the work, which almost explains itself. The labeled 
cylinders are of a known weight and are filled with soils whose water 
contents are known and the weight of each is taken. The frame from 
which the cylinders are suspended is lowered until each cjdinder 
is brought and kept in contact with the water in the trough below. 
When it is shown by repeated weighings that the respectiye soils haye 
taken up all the water the}" can, the weights are recorded, and from 
these data are calculated their absorptiye powers. The C3"linders are 
then kept suspended in the air, the water is remoyed from the trough, 




Fig. 1. — Apparatus used in observations on absorption and retention of moisture by soils. 

and the cylinders are reweighed at weekh" interyals, and from the 
data of the reweighings the retentiye powers of the soils are ascertained. 
The following table shows the results obtained. It should be under- 
stood that these soils are all of yolcanic origin and that they owe their 
extreme divergencies in physical properties, in the first place, to 
causes which date from the emission of the layas from the craters, and, 
in the second place, to the extreme variations of climatic conditions 
that exist locallj^ upon these islands. The table expresses, in the second 
column, the percentage of water absorbed b}" each soil, in the third 
column the water retained at the end of one month, and in the fourth 
column the water finall}^ retained: 



15 



Water absorbed and retained by Hmvaiian soils. 



Sample of soil. 


Water 
absorbed. 


Water re- 
tained at 
end of one 
month. 


Water re- 
tained at 
final deter- 
mination. 


1 


Per cent. 
31.8 
50.0 
51.0 
36.5 
59.5 
52.2 
47.0 
46.6 
52.2 
86.4 
72.7 
86.9 
73.7 
73.0 
70.0 
44.3 
46.3 
62.6 
45.2 


Per cent. 
12.4 
22.9 
19.6 
14.0 
29.3 
23.3 
21.9 
19.7 
20.2 
52.2 
48.4 
51.9 
4.5.9 
3S.6 
42.3 
14.8 
16.8 
29.1 
18.2 


Per cent. 
2.5 


■? 


8.0 


3 


5.5 


4 


5.6 


5 


14.7 


6 


7.7 


7 


8.4 


8 


6.4 


9 


9.4 


10 


28. 2 


11 


27.2 


12 


29.2 


13 


25. 2 


14 


21.1 


15 


22.1 


16 


5.4 


17 


6.5 


18 


14.3 


19 


8.9 







The last weighings were made five months from the beginnings of 
the tests. It was found that some, in fact most, of the soils were 
increasing again in weight with increasing dampness of the air in the 
room. 

The causes of the extreme variations in those soils in the matter of 
their power to take up and hold water are several, but the chief one 
is the result of local climatic conditions. In localities having small 
rainfall the growth of vegetation is small, and consequently the amount 
of vegetable matter which comes from the decay of plants in the soil 
is also small. In wet districts the opposite is the case. Rainfall 
means vegetation and copious plant growth means excess of organic 
matter in the soil as a result of vegetable decay, and excess of organic 
matter also means an excess of nitrogen in the soil, the nitrogen being 
a constant component of living and decaying plant organisms. The 
relation of the amount of nitrogen in the soil to the power to absorb 
and retain water is shown by the following figures, which give the 
average of 100 analj^ses of Hawaiian soils: 



Effect of nitrogen on moisture capacity of soils. 



Soil samples. 


Nitrogen 
content. 


Water 
absorbed. 


Water 
retained. 


Average of 50 


Per cent. 

0.163 

.647 


Per cent. 
44.6 
66.5 


Per cent. 
6 2 


Average of 50 


19 7 







Following the action of organic matter, the next most important 
factor in determining the power of soils to take up and hold water is 
the relative amount of clay, or of the elements which form clay, 
present in the soil. 



IG 

For the purpose of this discussion we are less concerned with the 
causes than with the fact that great variations actually exist in the 
relative powers of soils to take up and hold water. This fact places 
before us a clear demonstration of the absolute need of first determin- 
ing the absorptive power of each soil before the application of water. 



SALTS IN HAWAIIAN SOILS AND WATERS. 

Having considered some of the physical and phj^siological factors 
which affect the action and value of water in its relation to the produc- 
tion of crops, we proceed to matters bearing upon its use. 

The waters of the Hawaiian Islands are of excellent quality, pro- 
vided they do not come in contact with the sea inflow or with soils 
having high contents of salt, due to the overflow of the sea at some 
earlier period. In some localities, however, contamination by sea 
water has gone so far that the water is destructive to vegetable life. 
In most instances the deleterious agent is common salt; in others there is 
a mixture of common salt with chlorids of magnesium and calcium. 
The latter are most injurious to plant life and, in lowlands, lying 
almost level with the sea, where there are no means of getting these 
salts removed, their impregnation renders the soil useless. 

A considerable portion of the water supply for irrigation in the 
Hawaiian Islands is derived from the underground flow. Ground 
waters, on account of the considerable proportions of certain highly 
desirable elements they contain, may be very valuable for application 
to crops. On the other hand, because of the large amount of sub- 
stances inimical to plant life held in solution in some cases, they may 
be quite unfit for irrigation. Numerous instances of the unfitness of 
such waters for plant use are furnished by other countries, and special 
examples have been found by the writer upon the Hawaiian Islands. 

The salt present in Hawaiian soils and its effect upon sugar cane are 
shown in the following table: 

Salt found in Hawaiian sugar lands, and its effect upon sugar cane. 



Sample of soil. 


Location. 


Salt in 
soil. 


Condition of cane. 


1 


Highlands 


Per cent. 
0.061 
.063 
.050 
.059 
.129 
.130 
.155 
.181 
.181 
.460 
.832 
.223 


Normal. 


2 


do 


Do. 


3 


do 


Do. 


4 


do 


Do. 


5 




Not wholly healthy. 


6 


do 


Do. 




do 


Quite healthy and normal. 


8 


do 


Yellow in color. 


9 


do 


Do. 


10 


do 


Small, yellow, stunted. 


11 . . 


do 


Cane white and dying. 


12 


Sea bluff land 


Leaves bleached, cane small. 







17 

In soils containing over 0.15 per cent of salt, unless a liberal allow- 
ance of some vital element, such as nitrogen, is present to force on the 
growth, the sugar cane is liable to suffer. A further example is to 
hand showing the production of three parts of one field which con- 
tained different amounts of salt in the soil, the soil in other respects 
being identical: 

Effect of salt upon the growth of sugar cane. 



Field. 



First part . . 
Second part 
Third part . 



Salt in 
soil. 



Yield of 
sugar per 



Per cent. 

0.10 

.45 

1.00 



6.0 
1.5 
0.0 



But the salt content of the soil and its action upon the growing 
crop can be modified by the amount and quality of the water used in 
irrigation. "Sweet" water can carry the salt down out of reach of 
the cane roots, but if there is no outlet for the water through the sub- 
soil it will come up again by evaporation to the surface, bringing with 
it a greater excess of salt to deposit near the roots. " Sweet " soil can 
bear the use of water containing a considerable amount of salt, but 
brackish water, added to a soil of appreciable salt content, acts sud- 
denly and rigorously on the cane. An example of the great sensitive- 
ness of the sugar cane, and the ease with which it takes up salt from 
irrigation waters, is shown in the following record of observations 
made by the writer: 

Effect of salt upon sugar cane. 



Condition of water. 



Slightly brackish. 
Highly brackish. . 



Salt in 
waters. 



Per cent. 

0.125 

.223 



Salt in 
cane juice. 



Per cent. 
0.470 

.714 



Condition of 
cane. 



Growing. 
Dying. 



In this example the soils contained exactly the same quantities of 
salt, about 0.15 per cent, which is too high to come in contact with 
even the slightly brackish water without detriment to plants. The 
extreme sensitiveness, of the sugar cane to the salt content of waters 
is made very clear. From our present experience, the danger point 
should be placed at 0.14 per cent, or 100 grains of salt per imperial 
gallon. 

12066— No. 90—01 2 



18 



The following table gives some analyses of Hawaiian waters that 
are in constant use for sugar-cane irrigation: 

Analyses of Haivaiian waters. 



Constituents. 



Sample 
No. 1. 



Sample 
No. 2. 



Sample 
No. 3. 



Sample 
No. 4. 



Mean an- 
alysis of all 
Hawaiian 
streamsand 
springs. 



Silica 

Iron oxid and alumina 

Calcium oxid 

Magnesium oxid 

Potassium oxid 

Sodium oxid 

Chlorin 

Sulphuric acid 

Phosphoric acid 

Total solids 

Grains per gallon 



Per cent. 
0. 0030 
.0015 
.0015 
.0020 
.0010 
.0030 
.0070 
.0002 
.0000 



Per cent. 
0. 0076 
.0006 
.0076 
.0058 
.0006 
.009-1 
.0200 
.0033 
.0002 



Per cent. 
0. 0072 
.0004 
.0043 
. 0051 
.0008 
.0081 
.0178 
.0027 
.0001 



Per cent. 
0. 0026 
.0006 
.0012 
.0015 
.0005 
.0030 
.0041 
.0012 
.0001 



Per cent. 
0. 0023 
.0005 
.0015 
.0013 
.0005 
.0033 
.0040 
.0011 
.0001 



.0260 
18.4 



.0760 
53.5 



.0600 
4-2.4: 



.0190 
13.3 



.0200 
13.6 



Samples Nos. 2 and 3 were injuriously affected with salt to a slight 
degree. These samples were from wells at almost sea level and only a 
short distance back from the tide line. Waters have been analyzed 
which showed over 300 grains of salt per gallon, thus showing the 
infiltration of the sea water. The data that have been furnished demon- 
strates the primary importance of fully testing the qualities of waters 
drawn from sources near to the sea, and examples could be produced 
showing the enormous losses that have followed the ignoring of such 
tests. 

DUTY OF WATER. 

By the term "duty of water, "^ as used in this bulletin, is under- 
stood the volume of water that is required to mature a given crop in 
given conditions of soil and climate. That the duty of water can not 
be a definite factor, the water being in equal demand and rendering the 
same service in all locations, has been amply indicated by the facts 
stated in preceding paragraphs. It has been shown that there are loca- 
tions where the volume of water directly evaporated from the soil is 
double the amount removed in other locations and under totall}^ differ- 
ent conditions of climatic exposure and action. Further, it was shown 
that soils themselves var}^ extremely in their powers to take up and 
retain moisture, which affords another illustration of the factors that 
determine the service of applied water in relation to the crop. If a 
given volume of water is applied to a soil of low absorptive capacity 
and with a small retentive power, loss occurs by seepage on the one 
hand and hy extreme evaporation on the other, thus causing a large 
expenditure by the soil and a minimized service rendered to the crop. 

^For definition of this term as used in the irrigation investigations of this Depart- 
ment, see U. S. Dept. Agr., Office of Experiment Stations Bui. 86, p. 33. 



19 

Again, crops may vary between ver}^ wide extremes in the volumes of 
water they consume per unit of substance formed, and consequently in 
the volumes necessary to bring them to maturity. 

IRRIGATION PRACTICE ON THE HAWAIIAN ISLANDS. 

The chief crops that are grown hj the aid of artificial irrigation in 
Hawaii are rice and sugar cane. 

The lands used for rice are the lowest flats found at the outlets of 
valleys and close on the sea. Irrigation is practiced upon all these 
lands, but no means of determining the volume used per acre have been 
adopted, and data are not at hand bearing on the question. 

Sugar production is, relatively speaking, a recent matter so far as 
the present volume of production is concerned. So late even as 1880 
the output is recorded as being 30,000 tons, while the production last 
year (1899) was 282,807 tons. The part played by artificial irrigation 
in the production of the Hawaiian crop is seen from the following 
statement: 

Tons. 

Sugar grown by natural rainfall 116, 382 

Sugar grown by irrigation 166, 425 

The area to which water is artificially applied is yearly increasing, 
and in two years more than two-thirds of the crop, which is also vastly 
increasing, will be grown by aid of irrigation. 

The richest lands upon the islands are those lying toward and a 
little above sea level. In most of the districts, however, the rainfall 
over the low-lying lands, and especially upon the leeward side, is 
utterly insufficient to produce the sugar crop. Until the practice of 
irrigation was adopted these lowlands were useless, but now they are, 
beyond comparison, the richest and most productive. 

The primary source of water upon the Hawaiian Islands is rainfall. 
Two unfavorable conditions attend its precipitation: (1) The maximum 
quantity falls during the cool season, when the crops are not in a state 
of maximum growth and able to make use of it, and (2) the chief pre- 
cipitation is over the mountain areas, where the water falls, soaks down 
into the rock strata, and runs largely to the sea, unless arrested and 
returned to the land. An illustration of the variation of rainfall with 
altitude is afforded by the following table: 

Variation of rainfall ivith elevation. 







Rainfall at 






elevations 




Rainfall 


of 




at 


2,000-3,000 




sea level. 


feet 
(2i miles 
from sea). 




Inches. 


Inches. 


Honolulu (Oahu) 


32 
28 


118 
179 


Haua (Maui ) 





20 

The apparently disadvantageous circumstance of Tieavy precipitation 
at maximum elevations has been turned into a special advantage by 
engineering means. In certain districts the water is collected by small 
ditches over the mountain areas, where it falls, and is conducted by 
main ditches or b}" flumes down to the cane-bearing lands below, over 
which it is distributed by gravity. Where the rainfall can not be 
easily collected over the mountain areas, the water which sinks down 
into deep substrata is tapped and arrested at or near sea level, where 
it is found running toward the sea. In places where the lava rock 
strata run out before reaching the sea the water comes to the surface 
in springs, but the great body flows out or is held in underground 
reservoirs at varying depths, and has to be sought for by means of 
wells, from which the water is lifted and forced up to considerable 
elevations b}^ high-duty pumps, where it is distributed. 

The pumps that are in service on the islands are chiefly of American 
build, and are in some instances of large capacity. Their duties range 
from the small lifts of the centrifugal pumps to those raising 12,000,000 
gallons per 2i hours. (Pis. I and II.) 

The amount of water applied in the irrigation of Hawaiian sugar 
cane is controlled mainly by the volume of the supply. Concerning 
the volume that is considered necessary and that is taken as a basis of 
estimation in calculating the water required by any given plantation 
and the capacit}^ of the pumps necessary to lift and apply it, reference 
is had to the data contained in a report on investigations made in 1889 
by Messrs. J. D. Schuyler and G. F. Allardt, civil engineers.^ The 
data and the views contained in that report were made the bases of 
operations by the authorities quoted, and they are still the views and 
represent the practice of those men who were on plantations at the 
time of the publication of the report in 1889. Other views and other 
methods are now coming into practice which are based more largely 
upon the principles set forth in the earlier paragraphs of this report 
and upon results obtained in actual experiments in irrigation. These 
will be spoken of later. The report referred to says: 

It seems to be the general practice here [island of Oahu] to irrigate "plant" cane 
every three or four days for the first month after planting or until it has made a strong 
growth of root and stalk. After that a watering is given every seven days for a time, 
diminishing to one watering every ten days, which is continued for about fifteen 
months from the time of planting, or until the maturity of the cane. It is customary 
to cease irrigation from one to three months before cutting. If, as in some districts, 
the cane did not mature short of eighteen to twenty months from time of planting, 
the period of irrigation would be from fifteen to eighteen months. In making our 
estimate we have assumed that fifteen months of irrigation would be the average 
required for sugar cane on the leeward slopes of this island [Oahu]. Three water- 
ings per month is the least that is considered safe to apply to keep the cane growing 

^ "Water supply for irrigation on the Honouluili and Kahuku ranchos," Oakland, 
CaL, 1889, pp. 32; see also Special Consular Reports on Canals and Irrigation in. 
Foreign Countries, 1891, pp. 395-407. 



U, S Dept. of Agr., Bui. 90, Office of Expt. Stations. 



Plate I. 




U. S. Dept. of Agr., Bui, 90, Office of Expt. Stations. 



Plate II. 



o ^ 






3;? 




21 

without check. In localities corresponding in position and climate to Honouluili it 
is customary to maintain this periodical irrigation regardless of the rainfall. The 
rain may at times exceed the quantity applied artificially, but irrigation is performed 
as usual notwithstanding, in order that there shall be no break in the' waterings. It 
seems to be generally understood by all planters that the depth of each watering shall 
be at least an average of 3 to 4 inches over the whole surface. Where the intervals 
between waterings are ten days and the depth applied is 4 inches, 1 cubic foot of 
water per second will perform a duty of 59.5 acres. With intervals of seven days 
and the same depth of water applied, 1 cubic foot per second would irrigate but 41.6 
acres, or 55.5 acres if the depth applied is but 3 inches. 

At this place it may be convenient to state, for the use of persons 
who judge by the standard of rainfall, that 1 cubic foot of water per 
second is equal to a flow of 294,700,032 United States gallons in fifteen 
months, and that if this volume were applied to 41.6 acres that would 
be equal to 7,108,173 gallons per acre, or a rainfall of 210 inches per 
year and 262 inches to mature the crop. 

The report proceeds to give examples, and begins with the Hawaiian 
Commercial Company's plantation at Spreckelsville, island of Maui, 
of which it says: 

The record for the calendar year 1888 shows that there was delivered to the plan- 
tation the following quantity of water: 

Cubic feet. 

From the Haiku ditch 1,175,000,000 

_ From the Waihee ditch 919,000,000 

Total 2,094,000,000 

Or 15,700,000,000 gallons. The rainfall during this period was 19.08 inches. 
With this water there were irrigated 2,000 acres of "plant cane" and 600 acres of 
*'ratoons" (volunteer second crop). In addition, 400 acres of seed cane were irri- 
gated once a month, consuming a quantity roughly estimated at 70,000,000 cubic feet. 
The remaining 2,024,000,000 cubic feet would be equivalent to a constant average 
flow through the year of 64.18 cubic feet per second, which, divided into 2,600 acres, 
would appear to give an average duty of 40.5 acres per cubic foot per second, and to 
indicate that the mean depth applied was nearly 18 feet in the aggregate (22 feet, or 
264 inches, for the crop period of fifteen months). 

The report states that the explanation for "this seemingly low 
duty " may be found in the fact that the water was also used for cattle, 
domestic, and other purposes. 

Mr. Hugh Morrison, general manager of the plantation at Spreck- 
elsville, states, as an epitome of his experience, that 11,000 cubic feet 
per acre applied every seven days will produce the very best results 
in growing sugar cane. Covering the period of fifteen months already 
stated, that amount was equal to 5,318,200 gallons per acre, or a rain- 
fall of 197 inches, which with the 19.08 inches of actual rainfall 
makes a total of 216.08 inches to produce the crop. The report 
continues: 

Mr. Morrison further adds that it is almost impossible to put on too much water (of 
course within reasonable limits) , and that the more water is applied, without going to 
extremes, the greater the yield. He has obtained a yield as high as 10 tons of sugar 
per acre in localities sheltered from the wind. The average yield of 1888 on 2,000 



22 

acres of plant -cane was of tons of sugar per acre; the ratoon crop averaged 3 J tons 
per acre. * * * 

On the Waikiku plantation, island of Maui, where the water supply is very abun- 
dant and in excess of the needs of the plantation, the consumption is equal to a duty 
of about 50 acres per cubic foot per second on plant cane and 60 acres on ratoons. 

On the Hamakuapoko plantation, Maui, where the average annual rainfall is 
reported as 35.2 inches, the amount applied is stated by the superintendent, Mr. 
James Cowan, to be 10,890 cubic feet per acre to each watering. The intervals 
between waterings are seven days, and consequently the duty of water in continuous 
flow is 55.5 acres per cubic foot per second. 

This amount is equal to a depth of 195 inches, which, with the nat- 
ural fall of 35.2 inches of rain, is equivalent to a total rainfall of 
230.2 inches to mature the crop, or 184:.2 inches per annum. Contin- 
uing, the report saj^s: 

In making up these figures, however, Mr. Cowan qualified them by saying that 
they are for the full capacity of the ditch, which is not always full when required, 
and is only partially compensated for full flow by the rainfall. * * * The average 
yield of the plantation is given at 5.6 tons of sugar per acre for plant cane and 4 tons 
for ratoon crop. * * * He summarizes by stating that to raise 1 pound of sugar 
requires about 51.8 cubic feet of water. 

There are so many elements of uncertainty included within the fore- 
going statement that it must be considered as merely an approxima- 
tion to the truth. The report further states: 

On the Kekaha plantation, Kauai, water is obtained by pumping to a height of 
18 to 36 feet, an average of about 27 feet. The delivery of the water is contracted for 
at the rate of $35 per acre per annum. The contractor is required to deliver sufficient 
water to irrigate 700 acres every ten days to an average depth of 4 inches at each 
watering. The duty thus performed, presuming the quantity contracted for is fully 
delivered, Avould be 59J acres per cubic foot per second. The pumping is done dur- 
ing ten hours each day. "The three pumps require to have a capacity of 7,000,000 
gallons per day each. Coal costs $li^ per ton'at the pumps. A very unusual yield 
is reported from this plantation. Eatoon crops for seven consecutive years are said 
to have produced an average of 5 tons of sugar per acre each year. 

In summing up their observations, Messrs. Schujder and Allardt 
say that a greater duty than 60 acres per cubic foot per second can 
not possibly be considered safe; or in other words, at least 5,000,000 
gallons per acre are required to make the crop. 

The data and conclusions furnished by Schuyler and Allardt have 
been given at length, for the reason that they formed the basis of com- 
putations some ten years ago and are still 'followed by the older plan- 
tation authorities. During the past six months two persons who are 
connected with the opening up of new plantations assured the writer 
that those estimates " were not conservative enough to be safe, and 
that in their calculations and provisions they were providing for not 
less than 6,000,000 gallons of water per acre for the crop." The more 
conservative estimates of those gentlemen are not based upon any 
ascertained knowledge of the requirements of the soil and crop. They 
are merelv the result of a wish to be safe. As a consequence, when 



^ It now costs $10 per ton. 



U, S, Dept. of Agr., Bui. 90, Office of Ex(5t. Stations. 



Plate III. 




Fig. 1 .—Arrangement for Irrigating Plats at the Hawaiian Experiment Station. 




Fig. 2.— a Sugar Factory in Hawaii. 



23 

the basis of 6,000,000 gallons per acre for the crop becomes the prac- 
tice, some other gentlemen of conservative mind who also wish to be 
safe will appear who will think 7,000,000 gallons a necessary provi- 
sion. At present the practice upon the plantations is not resting upon 
ascertained requirements which can be arrived at only by the aid of a 
knowledge of the physical laws that have been set forth and by actual 
tests involving the determination of the amount of water that the crop 
during the different stages of growth requires in given conditions of 
soil and climate. 

STUDY OF IRRIGATION AT THE HAWAIIAN EXPERIMENT 

STATION. 

In view of the absence of established data bearing upon the actual 
requirement of the sugar cane in the conditions of soil and climate of 
the Hawaiian Islands, and also on account of the great variations that 
obtain in the practice of irrigation, the writer determined upon a 
series of tests which should be carried out along lines of strictly eco- 
nomic purpose, but controlled by the aid of such physical and chem- 
ical observations as were previously shown to underlie any system of 
rational irrigation. 

The Hawaiian Experiment Station is located in the suburbs of Hon- 
olulu and comprises 5 acres of land. In laying out the area into 
diAdsions and plats special provisions was made for the use of irriga- 
tion water. The water supply is that of the city municipality, and it 
is laid on by iron pipes with very numerous faucet discharges. The 
distribution is made by means of rubber hose, thus controlling the 
delivery at any place or time. (PL III.) 

The topography of the field is favorable for irrigation, its surface 
being relatively level. 

The soil is exclusively derived from the decomposition of basaltic 
lavas. There is a depth of 15 inches of tillable earth resting upon a 
porous subsoil, an understratum which is composed of chips of lava 
stone, scoria, and black sand. The total mass of soil is thus relatively 
small, 1 acre to the depth of 15 inches weighing 4,368,825 pounds. 
The constituents of the soil are shown in the following table: 

Analysis of soils at Hawaiian Experiment Station. 



Soil constituents. 



Moisture 

Combustible matter 

Insoluble silica 

Soluble silica 

Titanic acid (TiOg) 
Phosphoric acid... 

Sulphuric acid 

Carbonic dioxid... 

Chlorin 

Ferric oxid 



Amounts 
present. 



Per cent. 

9.526 

9.347 

16. 660 

17. 058 

2.460 

1.050 

.164 

.080 

Trace. 

23. 630 



Soil constituents. 



Ferrous oxid... 

Alumina 

Manganese oxid 

Lime 

Magnesia 

Soda..,o 

Potash 

Nitrogen 

Total 



Amounts 
present. 



Per cent. 
5.515 
12. 540 
.145 
.861 
.821 
.175 
.581 
.149 



99. 862 



24 



The power of this soil to take up water is 48.5 per cent. The cli- 
matic conditions have alread}^ been amply discussed, since the data 
contained in the earlier paragraphs of this work bearing upon the 
evaporation of moisture from water and soil surfaces and the trans- 
piration of water b}^ the sugar cane were all observed and recorded at 
this station. 

Bv the mode of appljdng water in use at the experiment station 
ever}-^ gallon of water that goes onto each experimental plat is meas- 
ured and recorded. This exactness is absolutely necessary not only in 
order to note the action of the water, but also that of other factors 
upon the development and results of the crop. Consequently the 
records of rainfall and the measurement of the water applied furnish 
the total water at the disposal of the crop in the course of its growth. 

Two crops of cane have already been grown upon the experiment 
station grounds by the aid of i-rrigation. The first crop was planted 
in Jul}', 1897, and harvested 20 months later. The second crop was 
planted late in June, 1898, and is now being taken off (March, 1900). 
The period of irrigation, however, extended from the time of planting 
until November of the following year, making some 17 months during 
which water was applied. Unless the weather is extremel}^ dry, the 
cane does not receive water several weeks 'previous to its being cut, 
in order to induce a more thorough ripening. Excess of moisture 
operates to keep the cane immature and indu<3es new shoots to appear 
and grow, thus injuring the crop. 

In the following table are recorded the amounts of water the crops 
received during the jea.rs specified as rainfall and by irrigation: 

Amounts of vjater received by crops at Hawaiian Ex'periment Station. 



Month. 


1897-98. 


1898-99. 


Rainfall. 


Irrigation. 


Rainfall. 


Irrigation. 


juiv ; 


Inches. 
0.63 
1.02 
4.12 
2.07 
2.11 

.88 

6.18 

8.04 

10.39 

1.21 

.84 
2.60 

.94 
1..58 

.88 
1.75 
1.32 


Inches. 
3.0 
8.0 
1.5 
3.5 
2.0 
3.5 
0.0 
1.0 
0.0 
1.0 
4.5 
2.0 
6.0 
5.5 
6.5 
4.5 
1.0 


Inches. 
0.94 
1.58 

.88 
1.75 
1.32 
1.86 
1.00 
3.75 
3.98 

.85 
2.01 

.88 

.17 
1.90 

.75 
2.92 

.47 


Inches. 

4.0 


August 


4 


September 


4.0 


October 


3 


November 


3 


December 


2 


January 


4 


February 


1.5 


March 


3.0 


April 


4.0 


May 


4 


June 


7.0 


July 


7.0 


August 


9.0 


September 


8.0 


October 


6.0 


November 


3.0 






Total 


46. 56 


48.0 


26.01 


76.5 







From the data in the rainfall columns it is seen that the most of the 
rain falls during the cooler months of the year, which are the months 
of minimum plant growth. This is a special climatic drawback. The 



U. S. Dept. of Agr., BuL 90, Office of Expt, Stations. 



Plate IV. 




25 

most advantageous combination of climatic conditions is the concur- 
rence of high temperature and maximum rainfall, or a moist, hot sea- 
son, and a dry, cool season, which combination occurs in the sugar 
zone of Queensland. It is very apparent that water does not possess 
a maximum value if it falls during the cool season and when the crop 
is not in full growth and able to make use of it. For this reason a 
less value, and importance have to be ascribed to the rainfall of these 
islands than might otherwise be. 

The table shows that, during the years 1898 and 1899, the rainfall 
covering the period of seventeen months was only 26.01 inches, or 18.3 
inches per annum. It should also be understood that the extra defi- 
ciency" in the rainfall can not be measured b}^ the simple amount of 
that deficiency, for the reason that, instead of the cloudy, wet days 
when the rain should have fallen, dry days of high evaporation 
occurred, thus aggravating the natural situation and causing a greater 
need for the water supplied by artificial means. When the totals of 
the data contained in the table are brought together, it is seen, how- 
ever, that the differences in the total amounts of water consumed by 
the respective crops are not material and no greater than has been 
reasonably accounted for. 



Total ivater received by tioo crops of sugar cane. 



Crop period. 


Rainfall. 


Irrigation. 


Total. 


1897-98... 


Inches. 
46.56 
26.01 


Inches. 
48 

77 


Inches. 
'94.56 


1898-99 


103. 01 







Before proceeding to furnish the full results of the two crops atten- 
tion may be called to the comparative value of the water which fell as 
rainfall and that of the water applied in irrigation, taking the sugar 
equivalent as the expression of value. It is possible to do this by the 
use of data obtained during the season 1897-98, when tests were carried 
out in the experiment field under identical conditions of soil, cultiva- 
tion, and fertilization. In these tests twent}" plats of cane were grown 
by the aid of irrigation in addition to the rainfall, and eight tests were 
made without any irrigation (PI. IV), the results being as follows: 

Yield of irrigated and unirrigated cane. 



Number of tests. 


Rainfall. 


Irrigation. 


Yield of 

sugar per 

acre. 


20 


Inches. 
46.56 
46.56 


Inches. 
48 


Pounds. 
24, 755 


8 


1,600 




Difference in favor of irrigation 










23 155 











26 

Nothing could show more conclusively than these figures the neces- 
sity of irrigation under the existing conditions, and the enormous 
sugar-equivalent value of irrigation water applied systematicallv to 
the cane during the season of maximum growth, which is the summer 
season. An equal volume of water falling in heavy rains during the 
cool season, when growth is slow, is largely lost through percolation 
and produces a comparatively small value in sugar. 

The following tables contain a statement of the crops of 1897-98 and 
1898-99 and of the value of the water applied by irrigation. A brief 
table is first given showing the average weight of cane and yields of 
sugar for the two seasons: 

Yield of cane and sugar at Hawaiian Experiment Station. 



Crop period. 


Number 
of tests. 


Yield of 

cane per 

acre. 


Yield of 

sugar per 

acre. 


1897-98 


20 
15 


Pounds. 
166, 562 
192, 440 


Pounds. 
24, 755 


1898-99 


27, 138 







These are the results in cane and sugar per acre of crops that were 
about nineteen months on the ground and subject to systematic irri- 
gation for seventeen months. 

The relation of the crops to the total volume of water received both 
as rainfall and by irrigation is as follows: 

Water required to produce 1 pound of sugar. 



Crop period. 


Rainfall. 


Irrigation. 


Water 
per acre. 


Yield of 

sugar per 

acre. 


Water re- 
quired to 
produce 1 
pound of 
sugar. 


1897-98 


Inches. 
46.56 
26.01 


Inches. 
48 
77 


Gallons. 

2,567,682 

2,797,133 


Pounds. 
24, 755 
27,133 


Pounds. 
865 


1898-99 


859 







The volumes of water consumed by the cane per pound of sugar made 
during the growth of the two crops are very nearly the same. During 
the growth of the crop of 1897-98 some of the rainfall occurred in 
heavy precipitations, and it was ascertained that water escaped through 
the subsoil and was lost. During the production of the crop of 1898-99 
none of the water received, either from rainfall or from irrigation, was 
lost in this manner. No single rainfall exceeded 1 inch, and in irri- 
gating no more than 1 inch of water was applied at any single watering. 

It is seen from the preceding tables that the maximum quantity of 
water applied artificially during a season of extreme drought was 77 
inches during a period of seventeen months, or 2,090,858 gallons of 
water per acre, to make a crop containing 27,133 pounds of pure sugar 
per acre. These results are the average of fifteen tests, which were 
made under identical conditions of soil, cultivation, and fertilization. 



27 

The following table brings together the estimates of the dut}" of 
water in the Hawaiian Islands contained in the report of Schuyler and 
AUardt/ previously referred to, and the results of experiments m^-de 
at the Hawaiian Experiment Station by the writer: 

Dutij of I rater in Haivaiian Islands. 



Water re- 
quired to 
produce 1 
pound of 
sugar. 



Water applied per 
acre per crop. 


Yield of 

sugar per 

acre. 


Depth. 


Quantity. 


Inches. 

262. 00 
216.00 
230. 20 
198.20 

94.56 

103. 01 


Gallons. 
7, 114, 348 
5, 865, 264 
6,250,850 
5,381,428 

2,567,682 
2,797,133 


Pounds. 
11, 100 
11,100 
11,300 
12,000 

24, 755 
27, 133 



According to Schuyler and»Allardt: 

Spreekelsville (1) 

Spreckelsville (2) 

Hamakuapoko 

Kekaha 

At the experiment station: 

First crop (1897-98) 

Second crop (1898-99) 



Pounds. 
5,345 
4,407 
4,613 
3,740 

865 
859 



In the above table the yields of sugar per acre as given are higher 
than stated by the plantation authorities. For Spreckelsville the yields 
as stated were "for plant cane, 5. 75 tons of sugar per acre; the ratoon 
crop, 3i tons per acre; " for Hamakuapoko, "5.6 tons of sugar per acre 
for plant cane and 4 tons for ratoon crops," and for ratoon crops at 
Kekaha "5 tons of sugar per acre for seven years." These figures 
express the amounts of sugar per acre obtained by the mills and mark- 
eted, and not the full amounts produced by the soil. As a correction, 
and to make the figures comparable with the statement of experiment- 
station yields, 20 per cent has been added to the amounts given by the 
plantations. This may be rather too much, but it has to be remembered 
that the mills ten years ago did not obtain as much sugar from the 
cane as they do to-day. However, the figures of yield as given are 
probably a little in favor of the plantations. 

In comparing the data contained in the table it is again to be remem- 
bered that the figures furnished by the plantations state what was 
actually being done by those plantations. The experiment-station 
data show what has been done and what it is possible to do, where the 
irrigation is carried out according to scientific principles and where 
the conditions are under control. Upon a large plantation the con- 
ditions can not be controlled to the same extent as is possible with 
experiments on limited, areas. This in no wise lessens the force of 
the fact that plantations are wasting huge volumes of water in their 
practice of irrigation or removes the necessitj^ of examining into and 
determining the location and causes of the waste. 

The figures contained in the last column of the table show the pounds 
of water received from rainfall and irrigation per pound of sugar 
grown. Instead of using sugar as the standard we may use the total 



^ Special Consular Reports on Canals and Irrigation in Foreign Countries, 1891, pp. 
396-398. 



28 

dry substance of the crops in its relation to the water received per 
acre. The exact data furnished by the station's experiments enable 
this to be done: 

Warer used to produce 1 jMund of dry substance. 



Crop period. 


Water re- 
ceived per 
acre. 


Drj' sub- 
stance 
produced 
per acre.i 


Water re- 
quired to 
produpe 1 
pound of 
dry sub- 
stance. 


1897_98. . .. 


Pounds. 
21,414,457 
23,328,089 


Pounds. 

98, 725 

110,087 


Pounds. 
216 


1898-99 


910 







iBy "dry substance produced per acre" is meant the total amounts of water-free cane and leaves 
produced by 1 acre of ground. During the crop period 1897-98 some rainfall water was lost by perco- 
lation through the subsoil, but how much was not ascertained. During the growth of the crop of 
1898-99 no water was lost. Two hundred and twelve pounds of water were used, therefore, to produce 
a pound of dry substance. 

The most fertile plantation upon the Hawaiian Islands last jear 
yielded 20,500 pounds of sugar per acre, and, according to the estimate 
of the manager, consumed a little oyer 5,000,000 gallons of water per 
acre. On this plantation a less yolume of water produced double the 
quantity of sugar that was obtained at Spreckelsyille and Hamakua- 
poko; consequently the waste of water at those places musthaye been 
great. Upon this fertile plantation, howeyer , there are ample eyidences 
of past excessive irrigation and waste. The yolume of water used per 
acre was double that used at the experiment station to produce less 
sugar per acre. 

A small crop of say 30 tons of cane or 4 tons of sugar per acre can 
not in its growth consume the yolume of water demanded by a crop 
of 80 tons of cane or 10 tons of sugar per acre. It can consume only 
a fixed portion of that yolume. The same principle applies in the 
demands made upon the soil for plant food. The large crop absorbs 
more of the soil constituents to compose its substance and promote its 
growth. Water is only one of the essential factors which control the 
size of the cane or other crop. The depth and fertility of the soil, the 
fertilizing elements supplied, and the extent of cultivation are all 
potent factors affecting production. It has already been shown in a 
previous paragraph that the growth of the cane and the amount of 
water used during increased growth, as indicated by the increased 
transpiration of water by the cane, are very noticeably influenced by 
the action of nitrogenous fertilizers, 

DISTRIBUTION OF WATER. 

In the Hawaiian Islands sugar cane is irrigated exclusively by means 
of ditches and furrows. In la34ng out a field to be planted in sugar 
cane the first step is to make a survey of the area and to determine its 
contour. The notes of the survey will show the direction in which the 
cane furrows shall be constructed and also show where the laterals 



29 



which feed the furrows yhould be located. On uneven ground the fur- 
rows are curved in order that the grade may be kept uniform. 

If a field is practically level — and there are vast areas of relatively 
level land in locations where cane sugar is likely to be grown — the 
furrows are dug straight through the field. The most level field, 
however, usually has a dominant decline in some direction which is 
usually determined by the general formation of the lands of the 
region. The Hawaiian Islands are of volcanic origin, and hence the 
general slope of the land is from the craters to the sea. The coun- 
try is mountainous in the neighborhood of the volcanoes. The 
slopes become flatter as lower levels are reached, until the decline 
apparently disappears in the lands bordering on the seacoast. The 



TT 



T 



t 



d- 



h 



J\[. 



^ 



■tfT* 



h- 



T-r 



Hsf- 



F^ 



d 



J'Vl 



1 



Main Water Ditch 



\\L 



Fig. 2.— Irrigation of sugar cane on level land by means of laterals. 

latter have been deposited by streams running from higher lands. 
In spite of the flat appearance of these lowlands they generally have 
a decline toward the sea which is not only sufficient to make the dis- 
tribution of water a simple matter, but also to effect the discharge of 
underground water. This, however, is not always the case, the writer 
having several tracts in mind where the ground water can not find a 
discharge owing to its surface being but slightly above the level of 
high tide. 

The diagram (fig. 2) shows a field that is furrowed for planting 
and has subditches dug for the distribution of water. The furrows 
are made at right angles to the fall of the land and the distributing 



30 

laterals are constructed at right angles to the furrows, or parallel 
with the natural water flow. 

As the diagram shows, the main ditch feeds the laterals and these 
feed the furrows. The laterals discharge into the furrows on each 
side, the water flowing one-half of the distance between laterals in each 
direction. The furrows in the diagram are between the rows of cane. 
In the Hawaiian Islands the cane is generallj" planted and kept in fur- 
rows and not ridged up, and the water is applied in those furrows, 
running in and out around the cane stalks. In other countries visited 
by the writer, where irrigation is required during a part of the grow- 
ing season, the cane is more generall}^ upon the ridge and the water is 
applied between the rows of the cane, as shown by the diagram. The 
practice is controlled by such factors as the nature of the soil, the 
rainfall at specific seasons, and the related questions of drainage. 

In the diagram (fig. 2), the lines indicating the rows of cane are 
assumed to be 5 feet apart, which is the usual distance. In some situ- 
ations, owing to local causes, the distance between the cane rows may 
be as much as 6 feet or as little as 4^ feet. The distance between the 
laterals is assumed to be 30 feet, which means that the water is intended 
to flow only 15 feet from each side of the laterals that are feeding the 
furrows. The lines running midway between but parallel with the 
laterals represent earth dams in the furrows. These limit the length of 
flow of the water from the laterals on each side. Only lands ha^dng 
a very even surface can be laid out upon the simple plan of the diagram. 

Before speaking in detail of the methods of applying water, one 
other sj'stem will be described. This provides for the direct discharge 
of the water from the main ditch into the furrows. The sj^stem 
(fig. 3) has been observed by the writer, its results considered, and it 
is mentioned chiefly to show its essential defects. 

In the system illustrated in this diagram (fig. 3), the water supplj-is 
from a main ditch of considerable size (a width of 5 to 8 feet has been 
observed), which feeds the water furrows between the rows of cane 
direct, as illustrated by the arrows in the diagram. The cane rows 
are drawn straight through the field. The water flows parallel with 
the rows of cane and not at right angles to them, as shown in diagram 
(fig. 2). Consequently the water has to distribute itself b}" flowing 
from the main ditch to the opposite end of the field. As already 
remarked, this sj^stem of distribution is exemplified in order to make 
clear its very palpable drawbacks, which will be briefly explained. 

Volume of the application. — Schujder and Allardt, in treating of 
this subject under the conditions of the Hawaiian Islands, state that 
" it seems to be generally understood by all planters that the depth 
of each watering, i. e., the volume of each application, shall be at 
the least an average of 3 to -4 inches over the whole surface of the 
ground." The same authors quote one of their witnesses as saj^ing 



31 

*' 11,000 cubic feet per acre every seven days will produce the very 
best results in growing sugar cane." That volume is equal to 3^ 
inches of water over the whole ground per weekly application. 
Another example from the same authority gives "10,890 cubic feet 
per acre to each watering every seven days." This volume is equal to 
an application of 3 inches of water over the whole ground once a 
week. When the small rainfall was added to the amounts applied by 
irrigation upon the plantations spoken of by Schuyler and AUardt, 



Main Water Ditoh 



-UtWVWtWtHWtMtVM- 



Fig. 3. — Irrigation of sugar cane on levelland by direct discharge of the water from 
the main ditch into the furrows. 

then the average application per seven days over the stated period of 
fifteen months or sixty-five weeks appeared as follows: 

Depth of ivater applied to sugar cane during sixty-five weeks {rainfall and irrigation). 



Plantation. 



Water 
applied 
per acre. 



Mean 
applica- 
tion per 

week. 



Sprecklesvllle (1) 
Sprecklesville (2) 
Hamakuapoko. . . 
Kekaha 



Inches. 
262.0 
216.0 
230.2 
198.2 



Inches. 
4.03 
3.32 
3.54 
3.05 



The figures in the outer column indicate the average depth of 
application per week during the growth of the crop, which is given as 
sixty-five weeks. Concerning the value placed upon the rainfall, 
Schuyler and AUardt say, "the rain may at times exceed the quantity 



32 

applied artificially, but irrig-ation is performed the same as usual, not- 
withstanding, in order that there shall be no break in the continuity 
of the waterings." 

Mode of application. — The two chief systems of applying irrigation 
water have already been spoken of: First, by flooding, and second, by 
furrow application (PL V). Two methods of appljdng water by the 
system of furrows have also been considered and illustrated (figs. 2 and 
3). For the present purpose we return to the method exemplified by 
fig. 2, or the system of a main ditch which feeds the laterals which in 
turn feed the furrows, the furrows being laid out at right angles to the 
laterals, which are drawn parallel with the natural slope of the land or 
with the water flow. As represented by fig. 2, the section of furrow 
between the laterals is assumed to be 30 feet in length, each lateral 
watering 15 feet on either side. This illustration is intended to exhibit 
an example of water distribution in the furrow that is highly 
efficient from the standpoint of utilization of the water. Upon 
many plantations, however, the method of feeding the furrows 
from both sides of the laterals is not in practice. Very frequently the 
water is let into the furrows from only one side of the laterals, although 
this practice is giving way. Again, the length of the section of fur- 
row along which the water has to flow, in present practice, varies from 
30 to 50 feet, sections 35 to 45 feet being the more common. 

The length of time that a given flow of water will require to reach 
the end of a furrow section, all other things being the same, will be in 
proportion to the length of the section; consequently, the length of 
time that the water must flow over the end of the section of furrow 
abutting the feeding lateral is decided by the time that the water 
requires to reach the farther end of the furrow. The other factors 
also controlling the length of time required to reach the whole length 
of the furrow are the volume of the stream, the slope of the ground, 
and porousness of the soil. When the soil is loose, as it is in furrows 
newl}^ made, the water travels slowly, it being absorbed b}^ the soil at 
the end of the furrow next to the inlet. The continued flow finally 
saturates the soil, and the water gradually travels along -thaioirrow- 
until it reaches the farther end, when, after a short time, it is shut off 
and turned into the next furrow. As the soil in the furrow becomes 
more solid and close with time the water travels more quickly, and the 
distribution tends to become somewhat more even, but in such a length 
of furrow the distribution never becomes uniform. The economic 
results of this uneven distribution are immediate, and as follows: The 
efi'ect of an excess of water at the end of the furrow next to the inlet 
upon the cane is first to retard the germination of the seed by largely 
excluding the air from the soil, without which incipient growth can not 
proceed. The eflect upon the cane continues and has been observed 
even up to its maturity. The action upon the soil is first seen in the 



U. S. Dept. of Agr., Bui 90, Office of Expt, Stations 



Plate V. 




33 

washing out of the soluble constituents upon which the crop depends 
for its nutrition. If the action is continued in lowlands where there is 
imperfect drainage, the mechanical state of the subsoil is seriously 
affected, becoming close and more impervious, which is due not only to 
the water but also to the carrying down of soluble alkaline salts. While 
these effects are taking place at the end of the furrow which receives the 
great excess of water, the 15 feet at the farther end is not receiving mois- 
ture enough for the requirements of the cane; the cane there is suffer- 
ing for want of water, and the 15 feet next to the inlet is suffering from 
an excess of water. The middle 15 feet in the section is the only por- 
tion which is receiving approximatel}^ an average of the quantity that 
is being applied. Were the sections of furrows only 15 feet long, with 
laterals feeding the furrows on each side, the distribution of the water 
would be relatively even over the whole surface of the ground. 

At the Hawaiian Experiment Station the land is relatively level. 
The furrows are parallel and are 5 feet apart. They are also divided 
into sections 10 feet in length for irrigation. At the first irrigation 
and afterwards, until the cane becomes too large for their use, the 
sections are divided by iron gates that are made to fit and block the 
furrow. Later, permanent divisions of earth are made. Each section 
of 10 feet receives, by actual measurement, its quota of water, the num- 
ber of gallons applied meaning either half an inch, 1 inch, or whatever 
is determined upon. By this system the ground receives uniformly 
the same depth of water. 

Returning briefly to diagram (fig. 2, p. 29), it can now be better indi- 
cated what the results are when this system is adopted. As will be 
remembered, the water is supplied directly by a main ditch. From it 
each furrow is fed, the water being let in and the flow continued until 
it reaches the farther end of the field, which in some cases is from 400 
to 600 yards distant. After the remarks already made upon the 
impossibility of an even distribution of water by furrows that are 
only 35 to 50 feet long, it is not necessary to consider in detail the 
results of pouring water into furrows until it traverses a length of 500 
yards. If the soil is porous, one-half of the field is soaked to ruin, 
while the farther half receives only half the water it could use. If 
the subsoil is close and impervious and the volume of water applied is 
near the average needed for uniform irrigation of the cane, the excess 
travels to the farther end of the field, where it stands and becomes 
stagnant. 

Frequency and i^olume of ap2?lication. — The volume of water to be 
applied and the frequency of the application are controlled by the 
crops being grown and the system of irrigation in use. The volume 
of water applied and the manner of applying it are factors which in 
one respect control the frequency of the application. If the sections 
of the furrows exceed a given length, say 15 feet, it will be impossible 
12066— No. 90—01 3 



34 

to apply a small volume, since the water would not reach the farther 
end of the furrow. If, however, we adopt a length of furrow not 
exceeding 15 feet, we then make it possible to lessen the volume of 
the application and yet secure good results by a more frequent appli- 
cation of the reduced volume. 

In considering the question of the volume of water that can be 
applied without loss, we are led back to a former paragraph where 
data are given upon the relative power of soils to absorb and retain 
moisture. These physical properties, however, are not the only fac- 
tors which determine the volume of water that an acre of land can 
hold and the volume of water that may be applied. The mass or depth 
of the soil is a still more significant factor. Deep soils, such as exist on 
these islands, where the depth may be 5 or more feet, can take up a 
large volume of water. Of course, if a large volume is repeated often 
enough and at short intervals, even such a soil will become saturated, 
and then the water will escape and be wasted. There are soils, however, 
and over considerable areas of the Hawaiian Islands, which are rela- 
tivelv ver}" thin, the depth varj^ng from, say, 8 to 15 inches. It is at 
once apparent that such soils, even if their absorptive power is up to 
the average, can not take up the same volume of water as the deeper 
soils spoken of, so that the escape and waste of water from them is 
not onW great but much more rapid. Moreover, when a shallow soil, 
we will say of 12 inches over the level, is furrowed out for planting* 
and irrigation, the depth of soil remaining at the bottoms of the fur- 
rows is reduced to about 6 inches. When the water is run into the 
bottom of the furrow it has merel}" 6 inches of soil to absorb it and 
prevent its escape. The soil of the ridges between the furrows, of 
course, could take care of the water if the latter were being spread 
over the surface of the whole ground, which is the case under natural 
rainfall. It has been observed, however, that the lateral absorption 
of the water by the ridges is relatively small compared with the ver- 
tical rate of absorption of the soil in the furrow bottom, to which 
force has to be added the action of gravity in drawing the water down. 

The volume of water that can be applied by irrigation without loss 
in Hawaiian soils has not been even approximately ascertained. In 
189 T certain tests were made at the Hawaiian Experiment Station in 
order to obtain some light on this question. These tests were carried 
out m}" means of a l3^simeter devised by the writer (PL VI), which 
ma}' be briefl}' described as follows: The lysimeter consists of drains 
44: inches deep with galvanized- iron gutters which discharge into a deep 
trench. At the end of each drain is a receiver that catches .an}' water 
which is in excess of what the soil can hold, and which consequently 
passes out through the drains. The soil that was removed for laying 
in the drains was put back and the drains were completed six months 
before the cane was to be planted, in order to restore the soil to its 
normal state. Six such drains were made as described, and cane was 



lU. S. Dept. of Agr., Bui. 90, Office of Expt. Stations. 



Plate VI. 




35 



planted upon five of these, the drains being 8 feet apart and 20 feet 
long-. The nature of the soil has been stated by the analysis in an 
earl}^ paragraph, and the depth is 15 inches, resting upon a porous and 
rather general silbsoil. The depth of the drains was made 44 inches, 
by which it is seen that some 30 inches of subsoil were cut through. 
Any water escaping through the soil and through the noncapillary 
subsoil to that depth it was safely assumed would be finally lost. 

When the cane was planted an equal quantity of water, but merely 
enough to start and keep the cane growing, was applied to each drain 
or row, this being continued until the cane was 1 foot high, when the 
actual tests began. 

The applications of water to five of the six drains were as follows, 
drain No. 1 being omitted: 

No. 2. Volume equal to one-half inch per week over the whole 
ground; application made everj^ seven daj^s. 

No. 3. Volume equal to 1 inch per week over the whole ground; 
application made every seven days. 

No. 4. Volume same as in No. 3; application 1.5 inches ever}^ ten 
daj's. 

No. 5. Volume same as in No. 4; application 2 inches every fourteen 
days. 

No. 6. Volume and application same as in No. 5. 

In No. 6 no cane was planted. 

The tests covered twelve weeks, and the results from the drains 
were as follows: 

Water apjjUed to drains, and the quantity lost. 



No. of drain. 


Total 

water 

applied. 


Amount and frequency of appli- 
cation. 


Total loss 

from 

drains. 


Ko. 2 


Gallons. 
408 
816 
816 
816 
816 




Gallons. 



No. 3 . . 


1 inch per 7 days 





No. 4 


H inches per 10 days 


32.3 


No. 5 


2 inches per 14 days 


131.3 


No. 6 


do 


272.3 









Drain No. 6 was a check, b}^ which is meant that while it was con- 
structed precisel}'- as the other drains no cane was planted upon it, in 
order to show b}^ comparison the actual work of the cane in prevent- 
ing the loss of water. As the table shows, Nos. 5 and 6 were watered 
exactl}" the same. They received an application ever}'^ fourteen days 
and a volume equal to 2 inches over the whole ground. No. 6 drain 
discharged 272.3 gallons, while No. 6 lost only 131.3 gallons, the dif- 
ference of 141 gallons being due to the retaining action of the growing 
cane. Bearing upon this matter of the water-holding action of the 
cane, it may be stated that drain No. 4, which received 1.5 inches of 
water every ten daj^s, lost the whole 32.3 gallons of the first and second 
applications when the cane was still ver}" young. After that period 



36 

the more-developed cane took care of all the water applied, none bemg' 
lost. The same action was observed with drain No. 5, which also lost 
the most of the 131.3 gallons hy drainage during the first three or four 
applications. These demonstrations of the increasing consumption of 
water by the crop with its increase of growth are in line with the deter- 
minations made with the cane grown in the tub. (See p. 10.) 

The results of the lysimeter tests are most valuable and to a degree 
very conclusive, but an objection may be raised to their complete con- 
clusiveness, due to the circumstance that the conditions were not those 
of normal, undrained land. The digging of the drains and the putting' 
back of the soil disturbed the natural state of the soil, rendering its 
condition difi'erent possibly from the field as a whole. In view of 
such possible objections to the results from the h^simeter, two more 
series of tests were begun, which are not j^et full}" concluded. The 
first series was conducted with plats of land one-twentieth of an acre 
in size, along which three rows of cane were planted. In these there 
was no disturbance of the soil whatever, no drains being made. At 
the end of the plats and opposite the middle cane row on each plat an 
observation hole was dug' to a depth of 50 inches. From this hole an 
iron pipe was driven in a length of 7 feet, 3 feet of the pipe reaching 
along under the cane row at the said depth of 50 inches. This arrange- 
ment was made in order to note the results of applying at regular inter- 
vals difi'erent volumes of water. The results were as follows: 



Water applied to cane crops, and the quantity lost. 



Plat. 


Depth of 
application 
per week. 


Volume 

applied per 

acre per 

week. 


Water lost. 


No. 1 


Inches. 
1 



3 


Gallons. 
27, 154 
54, 308 
81,462 


None. 


Ko.2 


Considerable. 


No. 3 


Enormous. 







It was not possible to determine directly the actual loss of water 
that took place, due to the fact that it sank down into the subsoil over 
a wide area and did not converge to any point of outlet. The pipes 
that were driven in discharged some water, but only a small proportion 
of what was being lost. This was proven by tunneling in to a depth 
of 1 foot under the pipes, a hole being made some S feet long and 
large enough for a man to creep up. After each irrigation water was 
found running down into the subsoil and draining out to lower levels. 
As a considerable discharge was taking place where 2 inches per week 
were being applied, even when the cane was 6 feet high, an idea is 
convcA^ed of the enormous waste that followed the application of 3 
inches per week. 

The second of this series of tests is still being carried on upon 3 
plats of land near bj^ the location of the first series. In this second 



37 

series the plan was made the same as in the tests with the h\simeter, a 
given volmiie of water being applied to each of the three plats, but 
with different intervals of time between the applications, as follows: 

'Water applied to cane in second test. 



Plat. 


Depth of application. 


Volume applied per 
acre. 


No. 22 


1 inch per 7 day.s 

2 inches per 14 days . . 

3 inches per 21 days . . 


Gallons. 
27,1.54 every 7 days. 
54 308 every 14 day.? 


No. 24 


No. 26 


81,462 every 21 days. 





These tests are being made under such conditions as prevail on a 
large scale upon plantations. In plat 22, which receives its water in 
weekl}" applications, the cane seed germinated three days earlier than 
where the heavier applications were made. On plat 26 the cane came 
up, not onl}^ slowly, but unevenl}^ and with a yellow, sicklj^ color. From 
the first and up to the time when the cane was nine months old the 
results of the weekly application were highly satisfactory. As was 
shown in the first of this series of tests, where a large application of 
water is made at one time the soil can not contain the whole of it, and 
a large portion drains into the subsoil and is lost. 

A very clear distinction has to be made between a rainfall of 3 
inches in depth, which falls during several hours and uniformly over 
the whole surface of the ground, and an irrigation equal to 3 inches in 
depth over the whole ground, which is not only applied in bulk within 
a few minutes, but the application of which is in a furrow comprising 
less than one-half of the total surface. In the latter case the phj^sical 
property of the soil — i. e.,its absorbent power — has comparatively no 
time to act and take up the water which is drawn down from the furrow 
bottom by gravit}^ and out of reach of the cane roots. On the other 
hand, the rain is distributed equally over the whole ground surface and 
ordinarily falls at such a rate that the soil particles can take up and hold 
it. Rainfall, of course, when the ground becomes saturated, behaves 
like irrigation water, and the excess seeps out below and runs away. 
In illustration of the different ways in which rainfall water and irriga- 
tion water behave, b}^ reason of the different modes of application, and 
of the phenomena which control these different behaviors, we give some 
data in detail from our experiment station records (lysimeter tests) : 

Comparative loss of water received from irrigation and from rainfall, drain No. 5. 



Pate. 



Depth and source of 
water received. 



Height 
of cane. 



Lost from 
drain. 



September 15 
September 19 
October 12 ... 
October 27 . . . 
October 28 . . . 



Inches. 
2, irrigation. 
2|-_, rainfall.. 
2, irrigation. 

do 

i, rainfall... 



Gallons. 
136 
158 
136 
136 
84 



Feet. 



Gallons. 
20. .50 
86.50 
27.50 
18.59 
8.25 



38 



Before discussing the data in the above table I shall give another 
table made up of the data attaching to No. 6 drain of the Ij^simeter: 

Comparative loss of water received from irrigation and from rainfall, drain No. 6. 



Date. 



Depth and source of Lost from 
water received. drain. 



September 15 . 
September 19 . 
October 12 ... , 

October 27 

October 28 ... , 



Inches. 
2, irrigation. 
2|-, rainfall.. 
2, irrigation. 

do 

i, rainfall... 



Gallons. 
136 
158 
136 
136 
34 



Gallons. 
25. 5 
91.5 
44.5 
36.5 
1.0 



If we compare the behaviors of drains Nos. 5 and 6 on the dates 
September 15 and 19, it is seen that No. 5 drain discharged consider- 
ably less water than No, 6. At that period there was enough of a 
root system developed in the cane to enable it to consume the water 
and to prevent its loss as compared with drain No. 6, where no cane 
was planted. On October 12 the water consumed hj the cane, which 
was notably larger, was evidently still greater, since No. 5 drain let 
only 27.5 gallons of water run out, against 41.5 gallons discharged by 
No. 6. On October 27 the water lost by No. 6 drain is just one-half 
of the volume given out by No. 6, while on September 15 No. 5 held 
back only one-fifth more water than No. 6, which was due to the small 
size of the cane on No. 5 at the earlier date. The next day, October 28, 
one-half inch of rain fell. Of course the soils of both drains Nos. 5 and 
6 were almost at the point of saturation. But it is seen what occurred: 
No. 5 lost 8 gallons out of the 31 gallons received, while No. 6 drain 
discharged merely 1 gallon. The result is reversed as compared with 
what took place on the dates September 15 and 19. In the first place 
we see the action of even the young cane in largely preventing the loss 
of water from the drains. When the cane is small its root system 
enables the soil of No. 5 to hold more of the rainfall water than was 
held back by No. 6. On October 28, however, the cane was much 
larger, its leaves almost spread from row to row, covering all the 
ground, and when even the small rainfall of half an inch fell the 
largely developed leaves of the cane gathered up the rain and con- 
ducted it directly to the cane roots in the furrow, where it sank down 
and out of the drains. The same amount of rain, but which fell evenly 
over the whole surface of row No. 6, was taken up more gradually by 
the soil and only 1 gallon of water discharged at the drain. 

The general conclusions to which the observations in detail have led 
may be expressed as follows: 

(1) A greater loss of water results from the application of a given 
volmne b}' irrigation than occurs when the same volume is received as 
rainfall. The exceptions to this rule are few, and are confined to 
examples of crops such as the sugar cane, having a large leaf surface, 
and which are planted in furrows. 



39 

(2) The application of a given volume of water per acre in furrows 
results in a greater loss and waste than where the same volume is 
applied by flooding the whole surface of the ground. 

(3) A greater loss of water from seepage takes place when a given 
volume is applied in large quantities at long intervals than when the 
same volume is applied in small quantities and frequently. 

SOME RESULTS OF OVERIRRIGATION. 

Effect on the soil. — From the foregoing considerations it is seen that 
soils can absorb and crops consume only so much water, and that when 
the applications are in excess of the requirements the surplus must 
sink into the substrata and be lost. The loss, however, is not covered 
by the mere waste of the water and the expenditures in getting it 
onto the ground; a further loss is caused by the action of the escaping 
water upon the soil and its constituents. Every gallon of water 
applied in excess of what the soil and crop can retain and use soaks 
away and is lost. In draining through the soil it dissolves and carries 
with it much of those bodies that are soluble in water, and as they are 
the constituents that the plant depends upon for its food, the excess 
of water acts as a plunderer and depleter of the elements of fertility 
of the soil. For these reasons the great damage that follows from 
excessive overirrigation can not be too strongly dwelt upon nor the 
practice too emphatically condemned. The more permanent injurious 
effects of the excessive application of water to soils and crops do not 
become apparent until the damage is done. Certain effects upon the 
young crop are soon visible and appear in the yellow color and stag- 
nation of growth. The field manager, however, who knows nothing 
of the physical and chemical properties of soils, of the relative require- 
ments of water by different crops and at the different stages of their 
development, does not conceive what is happening to the fertilizing 
elements applied for the use of the present crop and to the natural 
constituents of the soil upon which future crops must depend. That 
ignorance in this particular is costly is confirmed by much evidence 
from the owners of ruined land. 

The cit}^ of Honolulu is deluged by irrigation, which is not only 
impairing the sanitary conditions immediately around the dwellings, 
but is also leading to the formation of fresh water swamps, which in 
their turn are vitiating the general atmosphere of the place. 

In irrigating alkaline lands, the conditions and rules which must be 
observed differ from those which control the economic irrigation of 
sweet soils by sweet waters. If no more water is applied than 
the soil can hold and the crop can make use of, conditions highly 
unfavorable to plant life can be brought about. The water that is 
applied in descending in the soil, dissolves and holds in solution a 
large amount of the salts, and as the water returns to the surface in 
answer to the calls of evaporation and plant needs the salts are brought 



40 

up also and deposited in great excess in the upper stratum or on the 
surface of the soil. The same result can follow the application of salt 
waters to sweet soils, of which the writer has noted acute examples 
upon the Hawaiian Islands. The application of brackish waters or 
waters charged with chlorid of sodiuni, magnesium, and lime, even to 
soils free from deleterious salts, can result in such an accumulation of 
those bodies in the upper soil that our domestic plants will not grow. 
The only provision against trouble from the use of saline waters is to 
use enough to leach the soils and prevent accumulations. To do this 
perfect underdrainage is essential, and it is further essential to imme- 
diately restore to the soil the soluble elements of plant food that have 
been carried out by the water, along with the injurious salts, or the 
soil will presently" become washed out and sterile. Irrigation of salt 
or alkaline soils with saline waters is a special matter and demands 
special treatment, and its requirements must not be confused or mixed 
up with the factors that exist in normal situations which govern the 
irrigation of sweet soils with sweet waters. 

Upon the island of Hawaii, which is the largest island in the Hawai- 
ian group, there are several well-defined districts which are distin- 
guished b}^ var}' ing climatic conditions. In the district toward the 
north the average annual rainfall is some 52 inches; in the middle dis- 
trict the precipitation ranges some 25 inches greater; while in the wet 
district of Hilo the yearly rainfall is some 180 inches, or nearl}^ 15 
feet. Upon the other islands of the group similar variations in rain- 
fall are found, but these variations difier not only with the districts but 
also with the elevation of the land in the same location. Two examples 
may be cited of extreme variations in rainfall in the same district due 
to a difference in altitude. In the one, the rainfall at sea level was 30 
inches, while at an altitude of 900 feet it was 118 inches per year, and 
in the other it was 28 inches at the sea shore and l'^9 inches at a height 
2,800 feet up the mountain side. The following table gives the results 
of a partial anal3^sis of the soils taken from these different districts: 



Effect of rainfall upon composition of soils. 





Average 
rainfall. 


Chemical constituents of the soils. 


Land. 


Lime. 


Potash. 


Phosphoric 
acid. 


Nitrogen. 


Drv . 


Inches. 

60 

120 


Per cent. 

0.474 

.248 


Per cent. 

0. 324 

.270 


Per cent. 

0.248 

.243 


Per cint. 
0.176 


Wet 


.450 







These figures indicate that soils derived from the same lava rocks 
vary extremely in their chemical composition, and that the chemical 
difference is the result of the different climatic conditions. The great 
excess of rainfall over the wet lands has removed the soluble lime and 
potash, and at the same time has largely augmented the amount of 



41 



nitrogen, which element is brought from the air and stored up in the 
soil in the accumulated organic matter. A more specific example is 
found upon the island of Hawaii in the districts of Hilo and Kau. 
Hilo is located upon the humid side of the mountain, and the Kau dis- 
trict lies on the side of limited rainfall. The rainfall and composition 
of the soils are as follows: 

Effect of rainfall upon composition of soils. 



District. 



Kau (drv) . 
Hilo (wet). 



Average 
rainfall. 



Inches. 

66 

180 



Chemical constituents of the soils. 



Lime. Potash. P^fP'?^"^ Nitrogen 



Per cent. 

0.955 

.128 



Per cent. 

0.846 

.257 



Per cent. 

0.606 

.504 



Per cent. 

0. 505 

.840 



In the Hilo district the rainfall ranges between 160 inches and 210 
inches per annum. The table shows the great difference in the pro- 
portions of the important constituents in the soils of the two districts, 
all of which have been derived from the same basaltic lava rocks. The 
difference in the cane crops grown in the two districts is just as strik- 
ing. In the Kau district the lands are highly productive when the 
rainfall is enough to support growth. In the Hilo district the yield 
of sugar per acre is little more than one-half the crop of Kau in nor- 
mal seasons; and upon the higher lands in the district, where culti- 
vation of cane has gone on for some ten or fifteen years, the soils are 
so badly washed out that thej^ have ceased to produce remunerative 
crops, and great expense is being incurred to restore the depleted fer- 
tilitj^ From these examples we see the results of an unusually large 
precipitation falling upon the ground A'^ear after year. Frequently in 
the Hilo district deluges of water carry the earth bodily into the sea, 
reddening the ocean a mile out from its shores. The analyses of the 
soils show that the soluble plant-food elements have been removed, 
while the crops testify that such is the case. According to the data 
furnished by Schujder and Allardt, the Hawaiian plantations are striv- 
ing to appl}" by irrigation from 200 to 260 inches of water per^crop, 
with what results, according to the testimony of nature, will eventually 
be seen. 

The writer has been endeavoring to obtain evidence in detail by 
means of tests made at the experiment station, showing the effects of 
the excessive use of water upon the soil itself and upon the chemical 
fertilizers that are applied for the use of the crop. 

In the course of the tests made by means of the lysimeter for deter- 
mining the loss of water when given amounts were applied b}" irriga- 
tion, determinations were also made in one of the series of tests show- 
ing the elements contained in the wasted water which had been removed 
from the soil. In the following example is shown the volume of water 



42 

that drained out of the soil with the amounts of the more chemical ele- 
ments carried out in the water during a period of ninety days: 

Fertilizing constituents leached from the soil by excessive irrigation. 



Loss of 
water. 


Constituents removed from 1 
soil per acre. 


Lime. 


Potash. 


Nitrogen. 


Gallons. 
58,000 


Pounds. 
278 


Poimds. 
61 


Poiuids. 
117 



These amounts of the elements were taken out of the natural soil by 
the excess of water applied during the short period of ninet}^ days. The 
water that is escaping from a held of newly cultivated ground diii'ers 
greatl}^ from the drainage water of a whole district whose surface is 
largely made up of undisturbed grass, forest, or other similar growths. 
The ground coverings save the soil from the direct action of the water, 
and where the subsoil has remained undisturbed for a great length of 
time the percolating waters have wrought out their own channels of 
escape to the substrata, and the results are that the water escapes ver}- 
rapidlj^, but carries relatively little dissolved soil materials with it. 
It is just the opposite with water falling upon or being applied to 
f reshl}^ broken and cultivated soil. It reaches ever}" particle, saturat- 
ing and acting upon its soluble constituents, and, according to the 
length of time that the water occupies in passing through, is the 
amount of solid matter contained in the drainage. The great differ- 
ence in the amounts of solid matter contained in general drainage 
waters and in waters escaping from a newly broken soil in a high 
state of cultivation in the same district is as follows: 

Per cent. 

Solid matter in general drainage water 0. 0537 

Solid matter in water from fresh soil 7200 

These figures indicate that the amount and character of the solid 
matters contained in the drainage waters of a vast watershed can not 
be taken as showing the solid soil elements which are being leached 
out of cultivated areas by excess of water. It has also been observed 
that the water escaping from cropped fields that have laid still and 
have been irrigated regularl}^ for a considerable length of time does 
not contain as much solid matter as was found in the first 1 cachings 
from the fresh soil. In the course of time the water works its own 
minute channels of escape through cultivated grounds, when the water 
escapes more rapidly, but carries less material with it. In the lysimeter 
tests this action of the applied water in working down its own lines 
of escape became so very pronounced that the experiments had to be 
stopped until the drains were all renewed and the soil rendered homo- 
geneous again. 

The escaping water not only carries with it the elements of plant 



43 

food present in the natural soil; it also acts ruinously upon several of 
the elements contained in artificial fertilizers that are applied at great 
cost to growing crops. The following table shows the water and 
chemical elements contained in the water lost per acre during ninety 
days. In one test the ground was planted with cane; in the other the 
ground bore no crop. 

Chemical constituents contained in drainage ivater. 



Land. 


Loss of 
water. 


Loss of constituents per acre. 




Lime. 


Potash. 


Nitrogen. 




Gallons. 
57, 250 
92, 250 


Pounds. 

4C7 

1,140 


Pounds. 

73 

213 


Pounds. 
3''5 


Bare land ... 


561 







The first thing observed from these figures is the action of the grow- 
ing crop in reducing the loss of water, and consequently of the ferti- 
lizing elements. The loss, however, especially upon the land bearing 
no crop, is enormous. Yet this loss is not greater than has been 
observed in the open field and on a large scale. In the district of 
Hilo, Hawaii, already spoken of, the lime content in 1 acre of soil to 
the depth of 1 foot is less than 4,000 pounds. In the dry district of 
Kau, on the arid side of the mountain, the lime content is not less than 
35,000 pounds per acre to the same depth, thus indicating that some 
30,000 pounds of lime per acre have been leached out by the great 
rains. The considerable amounts of nitrogen leached out require no 
explanation, as the soluble and wasteful behavior of the nitrates is well 
known, as also the action of nitric and hydrochloric acids in plunder- 
ing the lime content of soils. These phenomena, then, exhibit very 
clearly the ruinous effects of excessive application of water upon 
natural soils and upon the artificial fertilizing elements that are ap- 
plied to crops. 

Effects of excess of water on crops. — The results to growing crops that 
follow heavy and continued rainfalls are matters of common experi- 
ence and often causes of widespread loss. No fact is more thoroughly 
established in agricultural experience than this one: That while a mod- 
erate rainfall is indispensable to growing crops, an excess of rain is 
the cause of immediate loss in the crop and of damage to the soil. In 
the wheat districts of Europe every farmer knows what he may expect 
from a dry spring; but if the month of May is wet as well as cool he 
also knows that the yield may be cut down bj' one-third. 

In the series of tests that were made at the Hawaiian Experiment 
Station CO determine the amount of water that could be applied to the 
cane in furrows before leaching and loss of water took place concur- 
rent observations were made upon the effect of applying different vol- 
umes of water upon the germination of the cane seed and the subse- 



44 

quent growth. The character of the soil of the three plats included in 
the test was the same. The cultivation and fertilization were also the 
same. The cane seed was all selected and each plat was planted the 
same daj'. At the time of planting and afterwards the plats received, 
respective!}^, 1 inch, 2 inches, and 3 inches of water per week and with 
the foUwing results: 

Plat 21. — One inch of water per week; cane found coming through 
the soil on the sixth day after planting. 

Plat 23. — Two inches of water per week; cane coming through the 
ground the eighth day after planting. 

Plat 25. — Three inches of water per week; cane coming through ten 
daj's after planting. 

It is thus seen that the cane seed receiving 1 inch of water per week 
germinated and came through the ground four days in advance of the 
cane seed receiving 3 inches of water per week. The relative number 
of the cane seeds that grew in the plats receiving the different volumes 
of water is shown in the following table: 

Number of plants germinated in plats receiving different quantities ofvxtter. 



Plat. 


Water 
applied 
weekly. 


Seed- 
pieces 
planted. 


Seed- 
pieces 
that 
grew. 


Seed- 
pieces 
that 
died. 


No. 21 


Inches. 
1 
2 
3 


802 
802 
802 


706 
698 
628 


96 


No. 23 


lOi 


No. 25 


17-1 







On October 1, four months after planting, the canes were all counted 
in each of the three plats, the number found being as follows: 

Number of canes groiuing at the end of four months in plats receiving different quantities of 

ivater. 



Date. 


No. of 
plat. 


Depth of 
water ap- 
plied per 
week. 


Number of 
canes in 
the plat. 




21 
23 
25 


Inches. 
1 
2 
3 


1,995 


Do 


1,701 


Do. 


1,599 







From the data contained in the previous tables and statements it is 
shown — 

(1) That the larger the volume of water applied to the planted cane 
seed in excess of 1 inch in depth the greater was the time required in 
germination. 

{'2) The greatest number of cane seeds died where the largest volume 
of water was applied. 

(3) The greatest number of canes was found four months after 
planting where the least volume of ^\ater was applied. 



45 

It is to be noted that the above data apply to the cane at the time of 
planting- and during- the early stages of growth. With greater devel- 
opment, and especially at the stage of maximum growth, the consump- 
tion of water will be considerably greater until 2 inches per week will 
be demanded. 

In the germination of the cane seed or of any other seeds the 
supremely essential factor is the oxygen of the air. Without the 
presence of the air and a moderate amount of moisture germination 
can not take place. On the other hand, when the ground is filled with 
water and kept in a saturated state, the air normally present in whole- 
some soils is driven out and replaced by the water; consequently the first 
essential to a rapid germination and growth is removed. Again, in 
the presence of an excess of moistui3 and a dearth of oxygen the 
germination is not only slow, but it can be stopped after having begun, 
and the seedling dies. These principles are illustrated in the tests 
already cited, where it is seen that the cane seed which received the 
great excess of water not only was four days longer in coming through 
the ground, but that a relatively larger proportion did not come up at all, 
having died in the ground. The application of an excess of water can 
also create another condition highly detrimental to a rapid and healthy 
germination. Irrigation water, which comes either from high alti- 
tudes or from underground wells, is generally very much cooler than 
the soil to which it is applied. In the tests made the temperature of 
the soil to a depth of 6 inches was 88° F. , while the water was 72° (the 
writer has found the temperature of some underground waters on the 
Hawaiian Islands to be 25° cooler than the air). The pouring on of a 
large excess of water of relatively low temperature immediately 
reduces the temperature of the soil, and thus makes another condition 
unfavorable to healthy germination and rapid growth. In cane-sugar 
countries, where the rainfall is liable to be considerable and the tem- 
perature of the soil is low at the time of planting, the cane seed will 
lie for weeks before coming up, and in unfavorable seasons much does 
not germinate at all. 

In one series of tests conducted by the writer, in which it was sought 
to include all factors conducive to growth and to avoid any unfavor- 
able conditions, the irrigation was begun and is being continued as 
follows: The seed was planted in dry and thoroughly cultivated and 
porous soil and sufficient water was applied to cover the ground to 
a depth of 1 inch. This amount was equal to a depth in the furrow, 
however, of 2.5 inches, which sank down and wet the soil to a depth 
of 6 or 8 inches below the seed bed. The application of 1 inch per 
week was repeated and continued for a period of four months. Not 
only at the time of germination, but even up to the end of three 
months after planting, the seed and the young cane could not consume 
anything like 1 inch of water per week. 



46 

Until the plant began to shade the ground considerable evaporation 
took place. The volume of water lost in this manner was much greater 
than that consumed bv the young plant. This was clearly shown by 
the results of evaporation and transpiration tests. With the increased 
development of the cane its consumption of water was greater, but the 
increased foliage protected the soil against the sun, and the loss of 
water from the soil itself became less. This demand for an equal 
volume of water each week was maintained until the crop was four 
months old, when the ground surface was completely covered b}" the 
cane foliage. At this time the crop was rapidly adding to its sub- 
stance. Cane stalks were well developed and the consumption of plant 
food and water was vastl}" augmented. In the fifth month of its age 
the appearance of the leaves showed that the cane required a some- 
what increased weekly allowance of water, and this was confirmed by 
the moisture found in the soil, which was down to 18.5 per cent. The 
soil in question has a capacity for taking up 48 per cent of its own 
weight of water, and the efiort is made to prevent the actual moisture 
in the soil from sinking below 20 per cent and from raising above 30 
per cent, the conditions of growth being most favorable when the 
moisture present in the soil is equal to about one-half of its maximum 
water-holding capacity. The exceptions to this rule are controlled by 
the temperature. In cool weather and low soil temperature the water 
in the soil should be kept low; in warm growing weather the moisture 
in the soil should be higher, but the point of saturation should never 
be reached or growth is impeded or stopped. In the fifth month more 
water was applied, the amount being increased to li inches per week. 
The cane could not bear the extra half inch every week, and alternate 
weeks only 1 inch was applied, until the greatly increased growth 
demanded not only li inches weekl}", but even 2 inches if the winds 
were yexj drying. 

As the cane gets older its root S3'stem develops proportionately, 
running not only in all lateral directions, but deeper where the soil 
allows. It is therefore good practice to increase the volume of irri- 
gation so that the soil moisture reaches as low as the roots penetrate. 
In fact, the moisture should be kept a little lower than the roots, in 
order to induce them to feed deeper. An extra irrigation of half an 
inch, and even an inch, may be given to be sure that the moisture 
content is maintained below. This moisture at a greater depth is not 
only required to cause the plant to feed deeper, but it is indispensable 
for the purpose of rendering the more insoluble matter of the subsoil 
soluble and read}-^ for the future use of crops. 

At the time this report is written the cane in the tests in question 
is ten months old. The cane stalks are some 8 feet in height, and the 
crop is so heavN^ that it lies nearly fiat and almost shuts out the sun. 
During a week of warm, sultrv weather it consumes 1.5 inches of 



47 

water. If the air is clear and warm, and a dr}' wind prevails, 2 inches 
per week are given; but if cool nights and average days prevail, only 
1 inch of water is given per week. The cane is in perfect health and 
growth; the moisture is maintained in the soil, as attested by the 
analyses; and no water escapes, as indicated by the observation drains. 
The object in irrigating sweet soils with sweet water is to meet the 
demands of soil evaporation and of transpiration b}- the crop, and to 
maintain an equilibrium of moisture in the soil relative to its maxi- 
mum water-holding capacity, and to avoid leaching and loss. 

SOME GENERAL OBSERVATIONS. 

In the course of annual visits of inspection made hj the writer to 
all districts upon the several islands of the Hawiian group during the 
past five years, ample opportunities have been afforded to observe the 
methods of irrigation in general practice and the results that have 
followed the application of water. There are districts, such as have 
been already described, where the temperatures are high and the 
rainfall verv small, and where crops could not be produced without 
the aid of irrigation. In most of these arid districts the soils are 
deep and of great fertilit}'^, which is largely due to the absence of 
heavy leaching rains, such as obtain in wet districts. The application 
of water to those deep, rich soils has resulted in the production of 
enormous crops. Those lands are still virgin so far as concerns the 
length of time they have been under cultivation, not more than four 
to eight crops having been taken off. It nvdy be that the present 
methods emploj^ed in irrigation will in time injure the land. If there 
is an}^ change in this respect it is not now evident. It is possible that 
overirrigation in certain localities, if not corrected, will render the 
lands nonfertile before the twentieth crop has been reached. The 
following paragraph is taken from the annual report of the present 
manager of one of the largest and most fertile plantations on Hawaii: 

It has come under our observation that the mechanical condition of the soil in 
the older fields, owing to the action of nitrate of soda (and heavy irrigation) , is 
not as good as that of virgin fields immediately adjoining. * * * It is apparent 
that any water passing through a soil, and beyond the cane roots, carries with it a 
certain amount of soluble matter, whether it consists of fertilizers applied or natural 
fertilizing elements in the soil. Therefore any water beyond that taken up by the 
cane is engaged in a leaching process that is detrimental. Thus, in spite of the gen- 
erous fertilizing that has been carried on upon this plantation, some of the older 
fields show a decrease in available potash and lime. 

The plantation here referred to is new, none of its lands having' pro- 
duced more than five crops. Since the lands were cultivated and the 
cane crops heavily irrigated evidences of excessive irrigation have 
made themselves clear. When the water is applied to the lands on the 
higher levels in excessive quantities the excess percolates through into 



48 - 'V^ 

the substrata, and reappears upon the surface of lands at lower levels. 
In this particular example numerous so-called " springs have broken 
out on the lands next to the sea since the irrigation of the fields above." 
Upon another island a manager of one of the plantations replied to the 
writer, in answer to questions: "Oh, yes; after every irrigation those 
gulches run a pretty good stream for the next twenty-four hours." 
The gulches in question are the low places to which the watersheds of 
the fields converge, and through which the excess of water applied in 
each irrigation finds its outlet to the sea. I have seen costly fertilizers, 
in bags, thrown into the ditches to be dissolved and distributed by the 
water, and consequently to be carried to the sea by the excess of water 
that found its way there. In another case the manager of the planta- 
tion said to the writer: 

So much water used to be run onto this field that it seeped out after every irriga- 
tion into the deep ditch running across the bottom end of the field; from that ditch 
it Avas turned into the field below and used over again. But now we put on less than 
half the former ciuantity and irrigate oftener, and there is no Avaste. 

In one other case the plantation manager remarked: 

We have had wonderfully fine springs of water in our low gulches since those 
upper lands have been irrigated. 

A few statements of a different kind have been received from plan- 
tation managers who were open to argument upon the methods of 
irrigation. One gentleman writes: 

The recovery of that field of ratoons from the horrible yellow state in which you 
saw it, and the yield of sugar, were due to lessening the supply of water before it was 
too late. 

Another manager wrote: 

The half of the field which has received just one-half of the usual allowance of 
water is better cane and the juice is of better quality than the cane upon the other 
part of the field getting the old amount of Avater. 

Unfortunately the number of these testimonials is small, most of the 
managers preferring to continue in the old way. A new factor, how- 
ever, is beginning to operate in certain districts. So much land is 
being devoted to sugar cane, causing an increased demand for water, 
that the suppl}^ is already' insufficient. It now appears that water will 
have to be ver}^ economicallj" handled in order to make it cover increas- 
ing demands. Economy in use is, therefore, a factor with which the 
managers of our irrigation matters will have to deal, and when that 
is accomplished, the daj^ of the scientific irrigator will have come. 



LB Mr '07 



/lX/^ 



